Julien Leuenberger,
Kristiāns Čerņevičs,
Oleg V. Yazyev
- As Moore's law approaches its fundamental limits, the development of nanoelectronic devices using low-dimension materials has become a promising avenue for further miniaturization and performance improvements. Among the various novel materials, graphene nanoribbons (GNRs) have emerged as particularly attractive candidates due to their unique electronic properties, opening up a whole new nanoelectronics paradigm consisting of circuits made entirely of graphene. However, due to the technical constraints that naturally arise when working on a two-dimensional plane, the design of efficient nanoelectronic components with a minimal spatial footprint remains a significant challenge. This dataset provides a comprehensive dataset of over 1'500 armchair GNR junctions or various sizes and shapes.
Latest version: v1
Publication date: Apr 18, 2024
Daniele Lanzoni,
Fabrizio Rovaris,
Luis Martín-Encinar,
Andrea Fantasia,
Roberto Bergamaschini,
Francesco Montalenti
- Machine Learning (ML) can be conveniently applied to continuum materials simulations, allowing for the investigation of larger systems and longer timescales, pushing the limits of tractable systems. Here we provide a comprehensive dataset of strained Ge films on Si and their corresponding strain states, which can be used to train a ML model capable of such acceleration. Approximately 80k 2D cases are included, reporting the profiles h(x) and the corresponding elastic energy densities and strain fields. The profiles are conveniently sampled using Perlin-noise and pure-sine waves. A 100nm-large computational domain is considered. The mechanical equilibrium problem is solved using Finite Element Method (FEM). Ge is modeled as an isotropic material and an eigenstrain of 3.99% is used, as in Ge/Si(001).
The database has been exploited for training a (fully) Convolutional Neural Network (CNN) which maps the free surface profile h(x) to the corresponding energy density. If plugged into ...
Latest version: v1
Publication date: Apr 18, 2024
Shubhajit Das,
Ruben Laplaza,
J. Terence Blaskovits,
Clemence Corminboeuf
- Frustrated Lewis pairs (FLPs), featuring reactive combinations of Lewis acids and Lewis bases, have been utilized for myriad metal-free homogeneous catalytic processes. Immobilizing the active Lewis sites to a solid support, especially to porous scaffolds, has shown great potential to ameliorate FLP catalysis by circumventing some of its inherent drawbacks, such as product separation and catalyst recyclability. Nevertheless, designing immobilized Lewis pair active sites (LPASs) is challenging due to the requirement of placing the donor and acceptor centers in appropriate geometric arrangements while maintaining the necessary chemical environment to perform catalysis, and clear design rules have not yet been established. In this work, we formulate simple guidelines to build highly active LPASs for direct catalytic hydrogenation of CO₂ through a large-scale screening of a diverse library of 25,000 immobilized FLPs.
The library is built by introducing boron-containing acidic sites ...
Latest version: v3
Publication date: Apr 17, 2024
Davide Tisi,
Federico Grasselli,
Lorenzo Gigli,
Michele Ceriotti
- The vast amount of computational studies on electrical conduction in solid-state electrolytes is not mirrored by comparable efforts addressing thermal conduction, which has been scarcely investigated despite its relevance to thermal management and (over)heating of batteries. The reason for this lies in the complexity of the calculations: on one hand, the diffusion of ionic charge carriers makes lattice methods formally unsuitable due to the lack of equilibrium atomic positions needed for normal-mode expansion. On the other hand, the prohibitive cost of large-scale molecular dynamics (MD) simulations of heat transport in large systems at ab initio levels has hindered the use of MD-based methods. In this work, we leverage recently developed machine-learning potentials targeting different ab initio functionals (PBEsol, r2SCAN, PBE0) and a state-of-the-art formulation of the Green-Kubo theory of heat transport in multicomponent systems to compute the thermal conductivity of a ...
Latest version: v1
Publication date: Apr 16, 2024
Yixiu Luo,
Juan Wang,
Luchao Sun,
Jingyang Wang
- Understanding the phononic origin of the infrared dielectric properties of yttria (Y₂O₃) and other rare-earth sesquioxides (RE₂O₃) is a fundamental task in the search of appropriate RE₂O₃ materials that serve particular infrared optical applications. We herein investigate the infrared dielectric properties of RE₂O₃ (RE = Y, Gd, Ho, Lu) using DFT-based phonon calculations and Lorentz oscillator model. The abundant IR-active optical phonon modes that are available for effective absorption of photons result in high reflectance of RE₂O₃, among which four IR-active modes originated from large distortions of REO₆ octahedra are found to contribute dominantly to the phonon dielectric constants. Particularly, the present calculation method by considering one-phonon absorption process is demonstrated with good reliability in predicting the infrared dielectric parameters of RE₂O₃ at the far-infrared as well as the vicinity of mid-infrared region, and the potential cutoff frequency/wavelength ...
Latest version: v1
Publication date: Apr 15, 2024
Andrea Fantasia,
F. Rovaris,
O. Abou El Kheir,
A. Marzegalli,
D. Lanzoni,
L. Pessina,
P. Xiao,
C. Zhou,
L. Li,
G. Henkelman,
E. Scalise,
F. Montalenti
- In a recent preprint, entitled: "Development of a machine learning interatomic potential for exploring pressure-dependent kinetics of phase transitions in Germanium", we presented a novel Neural-Network (NN) interatomic potential for Ge. We recall that Ge phases different from the cubic-diamond one are of particular interest for applications. Hexagonal Ge, for instance, displays superior optical properties. It is therefore important to investigate how, exploiting pressure, Ge can be transformed into different allotropes. In order to build a potential tackling kinetics of pressure-induced phase transformations, several kinetic paths (mainly sampled using the solid-state Nudged Elastic Band method) were added to the database, following a suitable active-learning procedure. Energies, forces, and stressed relative to the various configurations were computed ab initio using VASP with the PBE functional. The NN potential was trained using the Deep Potential Molecular Dynamic package ...
Latest version: v1
Publication date: Apr 11, 2024
Lorenzo Gigli,
Alexander Goscinski,
Michele Ceriotti,
Gareth A. Tribello
- The accurate description of the structural and thermodynamic properties of ferroelectrics has been one of the most remarkable achievements of Density Functional Theory (DFT). However, running large simulation cells with DFT is computationally demanding, while simulations of small cells are often plagued with non-physical effects that are a consequence of the system's finite size. Therefore, one is often forced to use empirical models that describe the physics of the material in terms of effective interaction terms, that are fitted using the results from DFT, to perform simulations that do not suffer from finite size effects. In this study we use a machine-learning (ML) potential trained on DFT, in combination with accelerated sampling techniques, to converge the thermodynamic properties of Barium Titanate (BTO) with first-principles accuracy and a full atomistic description. Our results indicate that the predicted Curie temperature depends strongly on the choice of DFT functional ...
Latest version: v1
Publication date: Apr 10, 2024
Eric Macke,
Iurii Timrov,
Nicola Marzari,
Lucio Colombi Ciacchi
- We present an orbital-resolved extension of the Hubbard U correction to density-functional theory (DFT). Compared to the conventional shell-averaged approach, the prediction of energetic, electronic and structural properties is strongly improved, particularly for compounds characterized by both localized and hybridized states in the Hubbard manifold. The numerical values of all Hubbard parameters are readily obtained from linear-response calculations. The relevance of this more refined approach is showcased by its application to bulk solids pyrite (FeS₂) and pyrolusite (β-MnO₂), as well as to six Fe(II) molecular complexes. Our findings indicate that a careful definition of Hubbard manifolds is indispensable for extending the applicability of DFT+U beyond its current boundaries. The present orbital-resolved scheme aims to provide a computationally undemanding yet accurate tool for electronic structure calculations of charge-transfer insulators, transition-metal (TM) complexes and ...
Latest version: v1
Publication date: Apr 08, 2024
Nicolas Roisin,
Guillaume Brunin,
Gian-Marco Rignanese,
Denis Flandre,
Jean-Pierre Raskin,
Samuel Poncé
- Strain engineering is a widely used technique for enhancing the mobility of charge carriers in semiconductors, but its effect is not fully understood. In this work, we perform first-principles calculations to explore the variations of the mobility of electrons and holes in silicon upon deformation by uniaxial strain up to 2% in the [100] crystal direction. We compute the π₁₁ and π₁₂ electron piezoresistances based on the low-strain change of resistivity with temperature in the range 200 K to 400 K, in excellent agreement with experiment. We also predict them for holes which were only measured at room temperature. Remarkably, for electrons in the transverse direction, we predict a minimum room-temperature mobility about 1200 cm²/Vs at 0.3% uniaxial tensile strain while we observe a monotonous increase of the longitudinal transport, reaching a value of 2200 cm²/Vs at high strain. We confirm these findings experimentally using four-point bending measurements, establishing the ...
Latest version: v3
Publication date: Apr 03, 2024
Jinzhen Huang,
Adam H. Clark,
Natasha Natasha Hales,
Camelia Nicoleta Borca,
Thomas Huthwelker,
Thomas J. Schmidt,
Emiliana Fabbri
- Doping and compositing are two universal design strategies used to engineer the electronic state of a material and mitigate its disadvantages. These two strategies have been extensively applied to the design of efficient electrocatalysts for water splitting. Using cobalt oxide (CoO) as a model catalyst, we prove that the oxygen evolution reaction (OER) performance could be progressively improved, first by Fe-doping to form Fe-CoO solid solution, and further by the addition of CeO2 to produce a Fe-CoO/CeO2 composite. X-ray adsorption spectroscopy (XAS) reveals that distinct electronic interactions are induced by the processes of doping and compositing. Fe-doping of CoO can break down the structural symmetry in the pristine material, changing the electronic structure of both Co and O species at the surface and decreasing the flat-band potential (Vfb). In comparison, subsequent compositing of Fe-CoO with CeO2 induces negligible electronic changes in the as-synthesized Fe-CoO (as seen ...
Latest version: v1
Publication date: Mar 26, 2024
Lorenzo Bastonero,
Nicola Marzari
- Infrared and Raman spectroscopies are ubiquitous techniques employed in many experimental laboratories, thanks to their fast and non-destructive nature able to capture materials' features as spectroscopic fingerprints. Nevertheless, these measurements frequently need theoretical support in order to unambiguously decipher and assign complex spectra. Linear-response theory provides an effective way to obtain the higher-order derivatives needed, but its applicability to modern exchange-correlation functionals remains limited. Here, we devise an automated, open-source, user-friendly approach based on ground-state density-functional theory and the electric enthalpy functional to allow seamless calculations of first-principles infrared and Raman spectra. By employing a finite-displacement and finite-field approach, we allow for the use of any functional, as well as an efficient treatment of large low-symmetry structures. Additionally, we propose a simple scheme for efficiently sampling ...
Latest version: v2
Publication date: Mar 22, 2024
Cameron Owen,
Steven Torrisi,
Yu Xie,
Simon Batzner,
Kyle Bystrom,
Jennifer Coulter,
Albert Musaelian,
Lixin Sun,
Boris Kozinsky
- This work examines challenges associated with the accuracy of machine-learned force fields (MLFFs) for bulk solid and liquid phases of d-block elements. In exhaustive detail, we contrast the performance of force, energy, and stress predictions across the transition metals for two leading MLFF models: a kernel-based atomic cluster expansion method implemented using sparse Gaussian processes (FLARE), and an equivariant message-passing neural network (NequIP). Early transition metals present higher relative errors and are more difficult to learn relative to late platinum- and coinage-group elements, and this trend persists across model architectures. Trends in complexity of interatomic interactions for different metals are revealed via comparison of the performance of representations with different many-body order and angular resolution. Using arguments based on perturbation theory on the occupied and unoccupied d states near the Fermi level, we determine that the large, sharp d ...
Latest version: v1
Publication date: Mar 22, 2024
Stefano Falletta,
Alfredo Pasquarello
- Through the use of the piecewise-linearity condition of the total energy, we correct the self-interaction for the study of polarons by constructing nonempirical functionals at the semilocal level of theory. We consider two functionals, the γDFT and the μDFT functionals, both of which are based on the addition of a weak local potential to the semilocal Hamiltonian to enforce the piecewise-linearity condition. We show that the resulting polaron properties are in good agreement with reference hybrid functional calculations. This supports the use of semilocal functionals for calculating polaron properties.
Latest version: v1
Publication date: Mar 19, 2024
Pengjie Shi,
Shizhe Feng,
Zhiping Xu
- A high-fidelity neural network-based force field (NN-F³) is developed to cover the space of strain states up to material failure and the non-equilibrium, intermediate nature of fracture. Simulations of fracture in 2D crystals using NN-F³ reveal spatial complexities from lattice-scale kinks to sample-scale patterns. We find that the fracture resistance cannot be captured by the energy densities of relaxed edges as used in the literature. Instead, the fracture patterns, critical stress intensity factors at the kinks, and energy densities of edges in the intermediate, unrelaxed states offer reasonable measures for the fracture toughness and its anisotropy.
Latest version: v4
Publication date: Mar 12, 2024
Xinhang Xu,
Chongchong Qi,
Xabier M. Aretxabaleta,
Chundi Ma,
Dino Spagnoli,
Hegoi Manzano
- Cement hydration is crucial for the strength development of cement-based materials; however, the mechanism that underlies this complex reaction remains poorly understood at the molecular level. An in-depth understanding of cement hydration is required for the development of environmentally friendly cement and consequently the reduction of carbon emissions in the cement industry. Here, we use molecular dynamics simulations with a reactive force field to investigate the initial hydration processes of tricalcium silicate (C₃S) and dicalcium silicate (C₂S) up to 40 ns. Our simulations provide theoretical support for the rapid initial hydration of C₃S compared to C₂S at the molecular level. The dissolution pathways of calcium ions in C₃S and C₂S are revealed, showing that, two dissolution processes are required for the complete dissolution of calcium ions in C₃S. Our findings promote the understanding of the calcium dissolution stage and serve as a valuable reference for the investigation of the initial cement hydration.
Latest version: v1
Publication date: Mar 11, 2024
Shilin Mao,
Yuting Cao,
Wei Chen,
Dongke Sun
- In this paper, we proposed a model coupling the lattice Boltzmann and the phase field methods with anisotropic effects is proposed, which is used to numerically describe the growth and movement of dendrites in rapid solidification of alloys. The model was applied to investigate the effects of dendrite movement and interfacial non-equilibrium on evolution of dendritic patterns for Si-9.0at%As and the CET for Al-3.0wt%Cu alloys. Both the growth and remelt processes of isolated dendrites are studied, and the result reveals the remelting influences on dendrite growth and solute micro-segregation in the condition of directional solidification. This dataset contains the underlying data for the above. This work demonstrates that the proposed model has a wide range of applicability and great potential to simulate the microstructure evolution with various solidification conditions.
Latest version: v1
Publication date: Mar 06, 2024
Arslan Mazitov,
Maximilian A. Springer,
Nataliya Lopanitsyna,
Guillaume Fraux,
Sandip De,
Michele Ceriotti
- High-entropy alloys (HEAs), containing several metallic elements in near-equimolar proportions, have long been of interest for their unique mechanical properties. More recently, they have emerged as a promising platform for the development of novel heterogeneous catalysts, because of the large design space, and the synergistic effects between their components. In this work we use a machine-learning potential that can model simultaneously up to 25 transition metals (d-block transition metals, excluding Tc, Cd, Re, Os and Hg) to study the tendency of different elements to segregate at the surface of a HEA.
In this record, we provide a dataset HEA25S, containing 10000 bulk HEA structures (Dataset O), 2640 HEA surface slabs (Dataset A), together with 1000 bulk and 1000 surface slabs snapshots from the molecular dynamics (MD) runs (Datasets B and C), and 500 MD snapshots of the 25 elements Cantor-style alloy surface slabs.
We also provide the HEA25-4-NN and HEA25S-4-NN final models, ...
Latest version: v2
Publication date: Mar 04, 2024
Yong Hu,
Junzhang Ma,
Yinxiang Li,
Yuxiao Jiang,
Dariusz Jakub Gawryluk,
Tianchen Hu,
Jérémie Teyssier,
Volodymyr Multian,
Zhouyi Yin,
Shuxiang Xu,
Soohyeon Shin,
Igor Plokhikh,
Xinloong Han,
Nicholas C. Plumb,
Yang Liu,
Jia-Xin Yin,
Zurab Guguchia,
Yue Zhao,
Andreas P. Schnyder,
Xianxin Wu,
Ekaterina Pomjakushina,
M. Zahid Hasan,
Nanlin Wang,
Ming Shi
- Charge density wave (CDW) orders in vanadium-based kagome metals have recently received tremendous attention, yet their origin remains a topic of debate. The discovery of ScV₆Sn₆, a bilayer kagome metal featuring an intriguing √3 x √3 x 3 CDW order, offers a novel platform to explore the underlying mechanism behind the unconventional CDW. Here, we combine high-resolution angle-resolved photoemission spectroscopy, Raman scattering and density functional theory to investigate the electronic structure and phonon modes of ScV₆Sn₆. We identify topologically nontrivial surface states and multiple van Hove singularities (VHSs) in the vicinity of the Fermi level, with one VHS aligning with the in-plane component of the CDW vector near the K ̅ point. Additionally, Raman measurements indicate a strong electron-phonon coupling, as evidenced by a two-phonon mode and new emergent modes. Our findings highlight the fundamental role of lattice degrees of freedom in promoting the CDW in ScV₆Sn₆.
Latest version: v1
Publication date: Mar 03, 2024
Lorenzo Gigli,
Davide Tisi,
Federico Grasselli,
Michele Ceriotti
- Lithium ortho-thiophosphate (Li₃PS₄) has emerged as a promising candidate for solid-state-electrolyte batteries, thanks to its highly conductive phases, cheap components, and large electrochemical stability range. Nonetheless, the microscopic mechanisms of Li-ion transport in Li₃PS₄ are far to be fully understood, the role of PS₄ dynamics in charge transport still being controversial. We build machine learning potentials targeting state-of-the-art DFT references (PBEsol, r²SCAN, and PBE0) to tackle this problem in all known phases of Li₃PS₄ (α, β and γ), for large system sizes and timescales. We discuss the physical origin of the observed superionic behavior of Li₃PS₄: the activation of PS₄ flipping drives a structural transition to a highly conductive phase, characterized by an increase of Li-site availability and by a drastic reduction in the activation energy of Li-ion diffusion. We also rule out any paddle-wheel effects of PS₄ tetrahedra in the superionic phases–previously ...
Latest version: v2
Publication date: Mar 01, 2024
Brenda S. Ferrari,
Matteo Manica,
Ronaldo Giro,
Teodoro Laino,
Mathias B. Steiner
- Polymers are candidate materials for a wide range of sustainability applications such as carbon capture and energy storage. However, computational polymer discovery lacks automated analysis of reaction pathways and stability assessment through retro-synthesis. Here, we report the first extension of transformer-based language models to polymerization reactions for both forward and retrosynthesis tasks. We curated a polymerization dataset for vinyl polymers covering reactions and retrosynthesis for representative homo-polymers and co-polymers. Overall, we report a forward model accuracy of 80% and a backward model accuracy of 60%. We further analyse the model performance on a set of case studies by providing polymerization and retro-synthesis examples and evaluating the model’s predictions quality from a materials science perspective.
Latest version: v2
Publication date: Feb 29, 2024
Cameron Owen,
Yu Xie,
Anders Johansson,
Lixin Sun,
Boris Kozinsky
- Metal surfaces have long been known to reconstruct, significantly influencing their structural and catalytic properties. Many key mechanistic aspects of these subtle transformations remain poorly understood due to limitations of previous simulation approaches. Using active learning of Bayesian machine-learned force fields trained from ab initio calculations, we enable large-scale molecular dynamics simulations to describe the thermodynamics and time evolution of the low-index mesoscopic surface reconstructions of Au (e.g., the Au(111)-`Herringbone,' Au(110)-(1x2)-`Missing-Row,' and Au(100)-`Quasi-Hexagonal' reconstructions). This capability yields direct atomistic understanding of the dynamic emergence of these surface states from their initial facets, providing previously inaccessible information such as nucleation kinetics and a complete mechanistic interpretation of reconstruction under the effects of strain and local deviations from the original stoichiometry. We successfully ...
Latest version: v1
Publication date: Feb 29, 2024
Peter Kraus,
Edan Bainglass,
Francisco F. Ramirez,
Enea Svaluto-Ferro,
Loris Ercole,
Benjamin Kunz,
Sebastiaan P. Huber,
Nukorn Plainpan,
Nicola Marzari,
Corsin Battaglia,
Giovanni Pizzi
- Compliance with good research data management practices means trust in the integrity of the data, and it is achievable by a full control of the data gathering process. In this work, we demonstrate tooling which bridges these two aspects, and illustrate its use in a case study of automated battery cycling. We successfully interface off-the-shelf battery cycling hardware with the computational workflow management software AiiDA, allowing us to control experiments, while ensuring trust in the data by tracking its provenance. We design user interfaces compatible with this tooling, which span the inventory, experiment design, and result analysis stages. Other features, including monitoring of workflows and import of externally generated and legacy data are also implemented. Finally, the full software stack required for this work is made available in a set of open-source packages.
Latest version: v2
Publication date: Feb 29, 2024
Omar Abou El Kheir,
Luigi Bonati,
Michele Parrinello,
Marco Bernasconi
- The phase change compound Ge₂Sb₂Te₅ (GST225) is exploited in advanced non-volatile electronic memories and in neuromorphic devices which both rely on a fast and reversible transition between the crystalline and amorphous phases induced by Joule heating. The crystallization kinetics of GST225 is a key functional feature for the operation of these devices. We report here on the development of a machine-learned interatomic potential for GST225 that allowed us to perform large scale molecular dynamics simulations (over 10000 atoms for over 100 ns) to uncover the details of the crystallization kinetics in a wide range of temperatures of interest for the programming of the devices. The potential is obtained by fitting with a deep neural network (NN) scheme a large quantum-mechanical database generated within Density Functional Theory. The availability of a highly efficient and yet highly accurate NN potential opens the possibility to simulate phase change materials at the length and time scales of the real devices.
Latest version: v2
Publication date: Feb 22, 2024
Maximilian E. Merkel,
Aria Mansouri Tehrani,
Claude Ederer
- We investigate the interplay of spin-orbit coupling, electronic correlations, and lattice distortions in the 5d¹ double perovskite Ba₂MgReO₆. Combining density-functional theory (DFT) and dynamical mean-field theory (DMFT), we establish the Mott-insulating character of Ba₂MgReO₆ in both its cubic and tetragonal paramagnetic phases. Despite substantial spin-orbit coupling, its impact on the formation of the insulating state is minimal, consistent with theoretical expectations for d¹ systems. We further characterize the electronic properties of the cubic and tetragonal phases by analyzing spectral functions and local occupations in terms of multipole moments centered on the Re sites. Our results confirm the presence of ferroically ordered z² quadrupoles in addition to the antiferroic x²-y²-type order. We compare two equivalent but complementary descriptions in terms of either effective Re-t2g frontier orbitals or more localized atomic-like Re-d and O-p orbitals. The former maps ...
Latest version: v1
Publication date: Feb 22, 2024
Edoardo Cignoni,
Divya Suman,
Jigyasa Nigam,
Lorenzo Cupellini,
Benedetta Mennucci,
Michele Ceriotti
- Data-driven techniques are increasingly used to replace electronic-structure calculations of matter. In this context, a relevant question is whether machine learning (ML) should be applied directly to predict the desired properties or be combined explicitly with physically-grounded operations. We present an example of an integrated modeling approach, in which a symmetry-adapted ML model of an effective Hamiltonian is trained to reproduce electronic excitations from a quantum-mechanical calculation. The resulting model can make predictions for molecules that are much larger and more complex than those that it is trained on, and allows for dramatic computational savings by indirectly targeting the outputs of well-converged calculations while using a parameterization corresponding to a minimal atom-centered basis. Our results on a comprehensive dataset of hydrocarbons emphasize the merits of intertwining data-driven techniques with physical approximations, improving the ...
Latest version: v2
Publication date: Feb 20, 2024
Dushko Kuzmanovski,
Jonathan Schmidt,
Nicola A. Spaldin,
Hendrik M. Rønnow,
Gabriel Aeppli,
Alexander V. Balatsky
- Dynamical perturbations modify the states of classical systems in surprising ways and give rise to important applications in science and technology. For example, Floquet engineering exploits the possibility of band formation in the frequency domain when a strong, periodic variation is imposed on parameters such as spring constants. We describe here Kapitza engineering, where a drive field oscillating at a frequency much higher than the characteristic frequencies for the linear response of a system changes the potential energy surface so much that maxima found at equilibrium become local minima, in precise analogy to the celebrated Kapitza pendulum where the unstable inverted configuration, with the mass above rather than below the fulcrum, actually becomes stable. Our starting point is a quantum field theory of the Ginzburg-Devonshire type, suitable for many condensed matter systems, including particularly ferroelectrics and quantum paralectrics such as the common substrate (for ...
Latest version: v1
Publication date: Feb 20, 2024
Chiara Cignarella,
Davide Campi,
Nicola Marzari
- One-dimensional materials have gained much attention in the last decades: from carbon nanotubes to ultrathin nanowires, to few-atom atomic chains, these can all display unique electronic properties and great potential for next-generation applications. Exfoliable bulk materials could naturally provide a source for one-dimensional wires with well defined structure and electronics. Here, we explore a database of one-dimensional materials that could be exfoliated from experimentally known three-dimensional Van-der-Waals compounds, searching metallic wires that are resilient to Peierls distortions and could act as vias or interconnects for future downscaled electronic devices. As the one-dimensional nature makes these wires particularly susceptible to dynamical instabilities, we carefully characterise vibrational properties to identify stable phases and characterize electronic and dynamical properties. Our search identifies several novel and stable wires; notably, we identify what ...
Latest version: v2
Publication date: Feb 15, 2024
Marco Di Giovannantonio,
Zijie Qiu,
Carlo A. Pignedoli,
Sobi Asako,
Pascal Ruffieux,
Klaus Müllen,
Akimitsu Narita,
Roman Fasel
- On-surface synthesis relies on carefully designed molecular precursors that are thermally activated to afford desired, covalently coupled architectures. In a recent publication, we studied the reactions of vinyl groups on poly-para-phenylene and provided a comprehensive description of all the reaction steps taking place on the Au(111) surface under ultrahigh vacuum conditions. We find that vinyl groups successfully cyclize with the phenylene rings in the ortho positions, forming a dimethyl-dihydroindenofluorene as the repeating unit, which can be further dehydrogenated to a dimethylene-dihydroindenofluorene structure. Interestingly, the obtained polymer can be transformed cleanly into thermodynamically stable polybenzo[k]tetraphene at higher temperature, involving a previously elusive pentagon-to-hexagon transformation via ring opening and rearrangement on a metal surface. Our insights into the reaction cascade unveil fundamental chemical processes involving vinyl groups on ...
Latest version: v1
Publication date: Feb 15, 2024
J.N. Graham,
C. Mielke III,
D. Das,
T. Morresi,
V. Ardakani,
A. Suter,
T. Prokscha,
H. Deng,
R. Khasanov,
S. D. Wilson,
A. C. Salinas,
Y. Zhong,
K. Okazaki,
Z. Wang,
M. Z. Hasan,
M. Fisher,
T. Neupert,
J.-X. Yin,
S. Sanna,
H. Luetkens,
Z. Salman,
P. Bonfà,
Z. Guguchia
- The AV₃Sb₅ kagome superconductors series are of intense interest due to their diverse and intricate properties. The breaking of time-reversal symmetry (TRS) in the normal state of these superconductors stands as a significant feature, yet the extent to which this effect can be tuned remains uncertain. Here, we employ a unique low-energy muon spin rotation technique combined with local field numerical analysis to study the TRS breaking response as a function of depth from the surface in single crystals of RbV₃Sb₅ with charge order and Cs(V0.86Ta0.14)₃Sb₅ without charge order. In the bulk (specifically above 30 nm from the sur face) of RbV₃Sb₅, we have detected a notable increase in the internal field width experienced by the muon ensemble. This increase occurs within the charge ordered state. Intriguingly, the muon spin relaxation rate is significantly enhanced near the surface of RbV₃Sb₅ (specifically within a depth range of 30-40 nm from the surface), and ...
Latest version: v1
Publication date: Feb 15, 2024
Kevin Janßen,
Philipp Rüßmann,
Sergej Liberda,
Michael Schleenvoigt,
Xiao Hou,
Abdur Rehman Jalil,
Florian Lentz,
Stefan Trellenkamp,
Benjamin Bennemann,
Erik Zimmermann,
Gregor Mussler,
Peter Schüffelgen,
Claus-Michael Schneider,
Stefan Blügel,
Detlev Grützmacher,
Lukasz Plucinski,
Thomas Schäpers
- With increasing interest in Majorana physics for possible quantum bit applications, a large interest has been developed to understand the properties of the interface between a s-type superconductor and a topological insulator. Up to this point the interface analysis was mainly focused on in-situ prepared Josephson junctions, which consist of two coupled single interfaces or to ex-situ fabricated single interface devices. In our work we utilize a novel fabrication process, combining selective area growth and shadow evaporation which allows the characterization of a single in-situ fabricated Nb/(Bi0.15Sb0.85)2Te3 nano interface. The resulting high interface transparency, is apparent by a zero bias conductance increase by a factor of 1.7. Furthermore, we present a comprehensive differential conductance analysis of our single in-situ interface for various magnetic fields, temperatures and gate voltages. Additionally, density functional ...
Latest version: v3
Publication date: Feb 15, 2024
Alexey Tal,
Thomas Bischoff,
Alfredo Pasquarello
- We demonstrate the importance of addressing the 𝚪 vertex and thus going beyond the GW approximation for achieving the energy levels of liquid water in many- body perturbation theory. In particular, we consider an effective vertex function in both the polarizability and the self-energy, which does not produce any computational overhead compared with the GW approximation. We yield the band gap, the ionization potential, and the electron affinity in good agreement with experiment and with a hybrid functional description. The achieved electronic structure and dielectric screening further lead to a good description of the optical absorption spectrum, as obtained through the solution of the Bethe–Salpeter equation. In particular, the experimental peak position of the exciton is accurately reproduced.
Latest version: v1
Publication date: Feb 14, 2024
Debdipto Acharya,
Omar Abou El Kheir,
Davide Campi,
Marco Bernasconi
- Superlattices made of alternating blocks of the phase change compound Sb₂Te₃ and of TiTe₂ confining layers have been recently proposed for applications in neuromorphic devices. The Sb₂Te₃/TiTe₂ heterostructure allows for a better control of multiple intermediate resistance states and for a lower drift with time of the electrical resistance of the amorphous phase. However, Sb₂Te₃ suffers from a low data retention due to a low crystallization temperature Tx. Substituting Sb₂Te₃ with a phase change compound with a higher Tx, such as GeTe, seems an interesting option in this respect. Nanoconfinement might, however, alters the crystallization kinetics with respect to the bulk. In this work, we investigated the crystallization process of GeTe nanoconfined in geometries mimicking GeTe/TiTe₂ superlattices by means of molecular dynamics simulations with a machine learning potential. The simulations reveal that nanoconfinement induces a mild reduction in the crystal ...
Latest version: v2
Publication date: Feb 12, 2024
Yann Muller,
Andrej Antusek,
Lars Jeurgens,
Vladyslav Turlo
- It is well known that interfaces in nanomaterials can act as ultra-fast short-circuit diffusion paths, as originating from local structural, chemical and/or electronic modifications at the interface. For example, the interface diffusivity of Cu in Cu/AlN nanomultilayers can be up to two orders of magnitude higher as compared to the bulk, which may promote interfacial premelting of Cu. Extensive ab initio calculations of vacancy formation and migration energies in Cu/AlN nanomultilayers were performed to arrive at the fundamental understanding of such anomalously fast interface diffusion phenomena. It was found that both the metallic Al-terminated interface and the mixed-bonded N-terminated interface promote high atomic interface mobilities by lowering the vacancy formation and vacancy migration energies in the interfacial Cu planes. Moreover, the out-of-plane vacancy migration energies highlights a strong tendency of vacancy segregation toward both interfaces.
Latest version: v1
Publication date: Feb 08, 2024
Xiushang Xu,
Amogh Kinikar,
Marco Di Giovannantonio,
Carlo Antonio Pignedoli,
Pascal Ruffieux,
Klaus Müllen,
Roman Fasel,
Akimitsu Narita
- On-surface synthesis has emerged as a powerful strategy to fabricate unprecedented forms of atomically precise graphene nanoribbons (GNRs). However, the on-surface synthesis of zigzag GNRs (ZGNR) has met with only limited success. In the paper where the data are discussed, we report the synthesis and on-surface reactions of 2,7-dibromo-9,9'-bianthryl as the precursor towards π-extended ZGNRs. Characterization by scanning tunneling microscopy and high-resolution noncontact atomic force microscopy clearly demonstrated the formation of anthracene-fused ZGNRs. Unique skeletal rearrangements were also observed, which could be explained by intramolecular Diels-Alder cycloaddition. Theoretical calculations of the electronic properties of the anthracene-fused ZGNRs revealed spin-polarized edge-states and a narrow bandgap of 0.20 eV.
Latest version: v1
Publication date: Feb 08, 2024
Jonathan Frassineti,
Pietro Bonfà,
Giuseppe Allodi,
Erik Garcia,
Rong Cong,
Brenden R. Ortiz,
Stephen D. Wilson,
Roberto De Renzi,
Vesna F. Mitrović,
Samuele Sanna
- The recently discovered vanadium-based Kagome metals AV₃Sb₅ (A = K, Rb, Cs) undergo a unique phase transition into charge-density wave (CDW) order which precedes both unconventional superconductivity and time-reversal symmetry breaking. Therefore the essential first step in building a full understanding of the role of CDW in establishing these unconventional phases is to unveil the symmetries and the microscopic nature of the charge-ordered phase. Here, we determine the exact structure of the 2×2×2 superlattice that develops below the charge-density wave ordering temperature (TCDW) in RbV₃Sb₅. We present a comprehensive set of ⁵¹V, ⁸⁷Rb, and ¹²¹Sb nuclear magnetic resonance (NMR) measurements and density functional theory simulations of NMR observables to provide a unique site-selective view into the local nature of the charge-ordered phase. The combination of these experimental results with simulations provides compelling evidence that the CDW structure prevailing below 103 K in ...
Latest version: v1
Publication date: Feb 05, 2024
Jinggang Lan,
Majed Chergui,
Alfredo Pasquarello
- Charge-transfer-to-solvent states in aqueous halides are ideal systems for studying the electron-transfer dynamics to the solvent involving a complex interplay between electronic excitation and solvent polarization. Despite extensive experimental investigations, a full picture of the charge-transfer-to-solvent dynamics has remained elusive. Here, we visualise the intricate interplay between the dynamics of the electron and the solvent polarization occurring in this process. Through the combined use of ab initio molecular dynamics and machine learning methods, we investigate the structure, dynamics and free energy as the excited electron evolves through the charge-transfer-to-solvent process, which we characterize as a sequence of states denoted charge-transfer-to-solvent, contact-pair, solvent-separated, and hydrated electron states, depending on the distance between the iodine and the excited electron. Our assignment of the charge-transfer-to-solvent states is supported by the ...
Latest version: v1
Publication date: Feb 05, 2024
Manaswini Sahoo,
Ifeanyi John Onuorah,
Laura Christina Folkers,
Evgueni Vladimirovich Chulkov,
Mikhail M. Otrokov,
Ziya S. Aliev,
Imamaddin R. Amiraslanov,
Anja Wolter-Giraud,
Bernd Büchner,
Laura Teresa Corredor Bohorquez,
Chennan Wang,
Zaher Salman,
Anna Isaeva,
Roberto De Renzi,
Giuseppe Allodi
- Magnetic topological insulators (TIs) promise a wealth of applications in spin-based technologies, relying on the novel quantum phenomena provided by their topological properties. Particularly promising is the (MnBi₂Te₄)(Bi₂Te₃)n layered family of established intrinsic magnetic TIs that can flexibly realize various magnetic orders and topological states. High tunability of this material platform is enabled by manganese–pnictogen intermixing, whose amounts and distribution patterns are controlled by synthetic conditions. Positive implication of the strong intermixing in MnSb₂Te₄ is the interlayer exchange coupling switching from antiferromagnetic to ferromagnetic, and the increasing magnetic critical temperature. On the other side, intermixing also implies atomic disorder which may be detrimental for applications. Here we employ nuclear magnetic resonance and muon spin spectroscopy, sensitive local probe techniques, to scrutinize the impact of the intermixing on the ...
Latest version: v1
Publication date: Jan 31, 2024
Fatemeh Haddadi,
Edward Linscott,
Iurii Timrov,
Nicola Marzari,
Marco Gibertini
- Hubbard-corrected density-functional theory has proven to be successful in addressing self-interaction errors in 3D magnetic materials. However, the effectiveness of this approach for 2D magnetic materials has not been extensively explored. Here, we use PBEsol+U and its extensions PBEsol+U+V to investigate the electronic, structural, and vibrational properties of 2D antiferromagnetic FePS₃ and ferromagnetic CrI₃, and compare the monolayers with their bulk counterparts. Hubbard parameters (on-site U and inter-site V) are computed self-consistently using density-functional perturbation theory, thus avoiding any empirical assumptions. We show that for FePS₃ the Hubbard corrections are crucial in obtaining the experimentally observed insulating state with the correct crystal symmetry, providing also vibrational frequencies in good agreement with Raman experiments. While empirical U can lead to an unstable ground-state (i.e. imaginary phonons), the system remains stable through the ...
Latest version: v1
Publication date: Jan 30, 2024
Agustin Salcedo,
Anastassia N. Alexandrova,
David Loffreda,
Carine Michel
- Achieving fine control over the dispersion of supported platinum nanoparticles (Pt) is a promising avenue to enhance their catalytic activity and selectivity. Experimental observations suggest that exposing ceria-supported Pt nanoparticles to O₂ at 500 °C promote their dispersion into smaller particles and eventually single atoms. In the associated paper we have combined several approaches and types of models in a consistent atomistic framework to evaluate the relative stability of ceria-supported Pt as a function of the degree of oxidation of Pt and of the particle size, ranging from single atoms to nanoparticles of 1.5 nm of diameter.
Latest version: v1
Publication date: Jan 29, 2024
N. Biniskos,
F. J. dos Santos,
M. dos Santos Dias,
S. Raymond,
K. Schmalzl,
P. Steffens,
J. Persson,
N. Marzari,
S. Blügel,
S. Lounis,
T. Brückel
- The metallic compound Mn5Si3 hosts a series of antiferromagnetic phases that can be controlled by external stimuli, such as temperature and magnetic field. In this work, we investigate the spin-excitation spectrum of bulk Mn5Si3 by combining inelastic neutron scattering measurements and density functional theory calculations. We study the evolution of the dynamical response under external parameters and demonstrate that the spin dynamics of each phase is robust against any combination of temperature and magnetic field. In particular, the high-energy spin dynamics is very characteristic of the different phases consisting of either spin waves or broad fluctuation patterns. This data set contains the data relevant to performing the spin dynamics simulations with the Spirit code, the spin-wave calculations with the SWIS code, and the neutron scattering experimental data.
Latest version: v1
Publication date: Jan 29, 2024
Maximilian M. Schmidt,
José Ruiz-Franco,
Steffen Bochenek,
Fabrizio Camerin,
Emanuela Zaccarelli,
Andrea Scotti
- In situ interfacial rheology and numerical simulations are used to investigate microgel monolayers in a wide range of packing fractions, ζ2D. The heterogeneous particle compressibility determines two flow regimes characterized by distinct master curves. To mimic the microgel architecture and reproduce experiments, an interaction potential combining a soft shoulder with the Hertzian model is introduced. In contrast to bulk conditions, the elastic moduli vary nonmonotonically with ζ2D at the interface, confirming long-sought predictions of reentrant behavior for Hertzian-like systems.
Latest version: v1
Publication date: Jan 24, 2024
Maximilian E. Merkel,
Claude Ederer
- We calculate the screened electron-electron interaction for the charge-disproportionated insulator CaFeO₃ using the constrained random-phase approximation (cRPA). While in many correlated materials, the formation of a Mott-insulating state is driven by a large local Coulomb repulsion, represented by the Hubbard U, several cases have been identified more recently where U is strongly screened and instead the Hund's interaction J dominates the physics. Our results confirm a strong screening of the local Coulomb repulsion U in CaFeO₃ whereas J is much less screened and can thus stabilize a charge-disproportionated insulating state. This is consistent with the case of the rare-earth nickelates where similar behavior has been demonstrated. In addition, we validate some common assumptions used for parametrizing the local electron-electron interaction in first-principles calculations based on density-functional theory (DFT), assess the dependence of the interaction on the choice of ...
Latest version: v1
Publication date: Jan 24, 2024
Andrea Ninarello,
José Ruiz-Franco,
Emanuela Zaccarelli
- Low-crosslinked polymer networks have recently been found to behave auxetically when subjected to small tensions, that is, their Poisson’s ratio ν becomes negative. In addition, for specific state points, numerical simulations revealed that diamond-like networks reach the limit of mechanical stability, exhibiting values of ν = −1, a condition that we define as hyper-auxeticity. This behavior is interesting per se for its consequences in materials science but is also appealing for fundamental physics because the mechanical instability is accompanied by evidence of criticality. In this work, we deepen our understanding of this phenomenon by performing a large set of equilibrium and stress–strain simulations in combination with phenomenological elasticity theory. The two approaches are found to be in good agreement, confirming the above results. We also extend our investigations to disordered polymer networks and find that the hyper-auxetic behavior also holds in this case, still ...
Latest version: v1
Publication date: Jan 24, 2024
Luis Martín-Encinar,
Daniele Lanzoni,
Andrea Fantasia,
Fabrizio Rovaris,
Roberto Bergamaschini,
Francesco Montalenti
- We develop a convolutional neural network (NN) approach able to predict the elastic contribution to chemical potential μₑ at the surface of a 2D strained film given its profile h(x). Arbitrary h(x) profiles are obtained by using a Perlin Noise generator and the corresponding μₑ profiles are calculated either by a Green's function approximation (GA) or by Finite Element Method (FEM). First, a large dataset is produced by exploiting the GA method and it is then used for the training of the NN model. The performance of the trained NN is extensively examined, demonstrating its ability to predict μₑ looking both to the training/validation set and to an additional testing set containing different profiles, including sinusoids, gaussians and sharp peaks never considered in the NN training. The NN is then applied to simulate the morphological evolution of strained Ge films, where the predicted μₑ at each integration timestep plays the role of driving force for material redistribution in ...
Latest version: v2
Publication date: Jan 23, 2024
Nanchen Dongfang,
Marcella Iannuzzi,
Yasmine Al-Hamdani
- The presence of defects, such as copper and oxygen vacancies, in cuprous oxide films determines their characteristic carrier conductivity and consequently their application as semiconducting systems. There are still open questions on the induced electronic re-distribution, including the formation of polarons. Indeed, to accurately reproduce the structural and electronic properties at the cuprous oxide surface, very large slab models and theoretical approaches that go beyond the standard generalized gradient corrected density functional theory are needed. In this work we investigate oxygen vacancies formed in proximity of a reconstructed Cu₂O(111) surface, where the outermost unsaturated copper atoms are removed, thus forming non-stoichiometric surface layers with copper vacancies. We address simultaneously surface and bulk properties by modelling a thick and symmetric slab, to find that hybrid exchange-correlation functionals are needed to describe the oxygen vacancy in this ...
Latest version: v1
Publication date: Jan 15, 2024
Qiang Chen,
Marco Di Giovannantonio,
Kristjan Eimre,
José I. Urgel,
Pascal Ruffieux,
Carlo A. Pignedoli,
Klaus Müllen,
Roman Fasel,
Akimitsu Narita
- On-surface synthesis serves as a powerful approach to construct π-conjugated carbon nanostructures that are not accessible by conventional wet chemistry. Nevertheless, this method has been limited by the types and numbers of available on-surface transformations. While the majority of successful cases exploit thermally triggered dehalogenative carbon–carbon coupling and cyclodehydrogenation, rearrangement of appropriate functional moieties has received limited research attention. In a recent work, we describe the unprecedented interchain coupling and thermally induced skeleton rearrangement of (dihydro)indeno[2,1-b]fluorene (IF) polymers on an Au(111) surface under ultrahigh vacuum conditions, leading to different ladder polymers as well as fully fused graphene nanoribbon segments containing pentagonal and heptagonal rings. Au-coordinated nanoribbons are also observed. All structures are unambiguously characterized by high-resolution scanning probe microscopy. The results provide ...
Latest version: v1
Publication date: Jan 09, 2024
Max Bommert,
Bruno Schuler,
Carlo A. Pignedoli,
Roland Widmer,
Oliver Gröning
- A detailed understanding of how molecules interact with two-dimensional materials, particularly concerning energy level alignment and charge transfer processes, is essential to incorporate functional molecular films into next-generation 2D material-organic hybrid devices. One of the major challenges in integrating molecular films in field-effect transistors is facilitating ambipolar charge transport, which is often hindered by the large electronic gap of the organic layers. In a recent work we compare the adsorption site-dependent energy level alignment of C60, C70, and C84 fullerenes induced by the spatial variation of the electrostatic surface potential of the h-BN/Rh(111) Moiré superstructure. As the size of the fullerenes increases, the HOMO-LUMO gap shrinks. In the case of C84, we find an intrinsic charge transfer from the substrate to the fullerenes adsorbed in the Moiré pore centers, rendering them negatively charged. The electric field effect-induced charging of neutral ...
Latest version: v1
Publication date: Jan 09, 2024
Masoud Rahbar Niazi,
W. A Curtin
- The poor ductility of hcp Mg is attributed to the low activity of non-basal slip systems and so activation of prismatic slip can aid ductility in rolled sheets by providing three additional <a> Burgers vector slip systems. Experimental studies show that dilute additions of alloying elements such as Zn and Al leads to softening of prismatic slip at low temperatures but strengthening at higher temperatures. Here, the role of solute strengthening of prismatic edge dislocations is investigated as a possible explanation for the higher-T strengthening. Mg-Zn is studied using first-principles inputs in a parameter-free solute strengthening theory. First-principles DFT is necessary to accurately assess the strong solute chemical interaction energies in the core of the compact edge dislocation. Such calculations are subtle due to motion of the dislocation in the presence of the solute, and methods to obtain reliable results with acceptable computational cost are discussed. While ...
Latest version: v1
Publication date: Jan 09, 2024
Andres Tellez-Mora,
Xu He,
Eric Bousquet,
Ludger Wirtz,
Aldo Romero
- We present a self-consistent method based on first-principles calculations to determine the magnetic ground state of materials, regardless of their dimensionality. Our methodology is founded on satisfying the stability conditions derived from the linear spin wave theory (LSWT) by optimizing the magnetic structure iteratively. We demonstrate the effectiveness of our method by successfully predicting the experimental magnetic structures of NiO, FePS₃, FeP, MnF₂, FeCl₂, and CuO. In each case, we compared our results with available experimental data and existing theoretical calculations reported in the literature. Finally, we discuss the validity of the method and the possible extensions.
Latest version: v1
Publication date: Jan 08, 2024
Blair Connelly,
Patrick Taylor,
George de Coster
- We present evidence of a strong circular photon drag effect (PDE) in topological insulators (TIs) through the observation of threefold rotationally symmetric helicity-dependent topological photocurrents using THz spectroscopy in epitaxially-grown Bi₂Se₃ with reduced crystallographic twinning. We establish how twinned domains introduce competing nonlinear optical (NLO) responses inherent to the crystal structure that obscure geometry-sensitive optical processes through the introduction of a spurious mirror symmetry. Minimizing the twinning defect reveals strong NLO response currents whose magnitude and direction depend on the alignment of the excitation to the crystal axes and follow the threefold rotational symmetry of the crystal. Notably, photocurrents arising from helical light reverse direction for left/right circular polarizations and maintain a strong azimuthal dependence—a result uniquely attributable to the circular PDE, where the photon momentum acts as an applied ...
Latest version: v1
Publication date: Jan 05, 2024
Enrico Di Lucente,
Michele Simoncelli,
Nicola Marzari
- Skutterudites are crystals with a cagelike structure that can be augmented with filler atoms (“rattlers”), usually leading to a reduction in thermal conductivity that can be exploited for thermoelectric applications. Here, we leverage the recently introduced Wigner formulation of thermal transport to elucidate the microscopic physics underlying heat conduction in skutterudites, showing that filler atoms can drive a crossover from the Boltzmann to the Wigner regimes of thermal transport, i.e., from particlelike conduction to wavelike tunneling. At temperatures where the thermoelectric efficiency of skutterudites is largest, wavelike tunneling can become comparable to particlelike propagation. We define a Boltzmann deviation descriptor able to differentiate the two regimes and relate the competition between the two mechanisms to the materials' chemistry, providing a design strategy to select rattlers and identify optimal compositions for thermoelectric applications.
Latest version: v1
Publication date: Jan 05, 2024
Kewei Tang,
Weihong Qi,
Guoliang Ru,
Weimin Liu
- Two-dimensional materials are excellent lubricants with inherent advantages. However, superlubricity has only been reported in a few of them. It is a regret that other promising 2D materials with different physical properties cannot be discovered and applied in production so that energy consumption can be greatly reduced. Here we carry out high-throughput calculations for 1475 two-dimensional materials and screen for low-friction ones. To set a standard, we propose, for the first time, a geometry-independent frictional figure of merit based on the condition for stick-slip transition and our theory of Moiré friction. For the efficient calculation of this figure of merit, an innovative approach is developed based on an improved registry index model. Through the calculation, 340 materials are found to have a figure of merit lower than 10-3. Eventually, a small set of 21 materials with a figure of merit lower than 10-4 are screened out within them. These materials can provide ...
Latest version: v1
Publication date: Dec 21, 2023
Amogh Kinikar,
Xiao-Ye Wang,
Marco Di Giovannantonio,
José I. Urgel,
Pengcai Liu,
Kristjan Eimre,
Carlo Antonio Pignedoli,
Samuel Stolz,
Max Bommert,
Shantanu Mishra,
Qiang Sun,
Roland Widmer,
Zijie Qiu,
Akimitsu Narita,
Klaus Müllen,
Pascal Ruffieux,
Roman Fasel
- Surface-catalyzed reactions have been used to synthesize carbon nanomaterials with atomically pre-defined structures. The recent discovery of a gold surface-catalyzed [3+3] cycloaromatization of isopropyl substituted arenes has enabled the on-surface synthesis of arylene-phenylene copolymers, where the surface activates the isopropyl substituents to form phenylene rings by intermolecular coupling. However, the resulting polymers suffered from undesired cross-linking when more than two molecules reacted at a single site. In the manuscript in which this data is discussed we show that such cross-links can be prevented through steric protection by attaching the isopropyl groups to larger arene cores. Upon thermal activation of isopropyl-substituted 8,9-dioxa-8a-borabenzo[fg]tetracene on Au(111), cycloaromatization is observed to occur exclusively between two molecules. The cycloaromatization intermediate formed by the covalent linking of two molecules is prevented from reacting with ...
Latest version: v1
Publication date: Dec 20, 2023
Estefanía Fernández Villanueva,
Pablo Germán Lustemberg,
Minjie Zhao,
Jose Soriano,
Patricia Concepción,
María Verónica Ganduglia Pirovano
- The CO₂ hydrogenation reaction to produce methanol holds great significance as it contributes to achieving a CO₂-neutral economy. Previous research identified isolated Cu⁺ species doping the oxide surface of a Cu-MgO-Al₂O₃ mixed oxide derived from a hydrotalcite precursor as the active site in CO₂ hydrogenation, stabilizing monodentate formate species as a crucial intermediate in methanol synthesis. In this work, we present a molecular-level understanding of how surface water and hydroxyl groups play a crucial role in facilitating spontaneous CO₂ activation at Cu⁺ sites and the formation of monodentate formate species. The computational evidence has been experimentally validated by comparing the catalytic performance of the Cu-MgO-Al₂O₃ catalyst with hydroxyl groups against its hydrophobic counterpart, where hydroxyl groups are blocked using an esterification method. Our work highlights the synergistic effect between doped Cu⁺ ions and adjacent hydroxyl groups, both of which serve ...
Latest version: v1
Publication date: Dec 20, 2023
David W. Tam,
Nicola Colonna,
Fatima Alarab,
Vladimir Strocov,
Dariusz Jakub Gawryluk,
Ekaterina Pomjakushina,
Michel Kenzelmann
- We present high-quality angle-resolved photoemission (ARPES) and density functional theory calculations (DFT+U) of SmCoIn₅. We find broad agreement with previously published studies of LaCoIn₅ and CeCoIn₅, confirming that the Sm 4f electrons are mostly localized. Nevertheless, our model is consistent with an additional delocalized Sm component, stemming from hybridization between the 4f electrons and the metallic bands at “hot spot” positions in the Brillouin zone. The dominant hot spot, called γz, is similar to a source of delocalized f states found in previous experimental and theoretical studies of CeCoIn₅. In this work, we identify and focus on the role of geometric frustration in exploring the relationship between heavy quasiparticles and the magnetically ordered ground state of SmCoIn₅. Specifically, we find a globally flat band consisting of Co 3dxy/3dz2 orbital states near E = −0.7 eV, indicating a general role for geometric frustration in the “115” ...
Latest version: v1
Publication date: Dec 19, 2023
Mingda Ding,
Taiki Inoue,
John Isaac Enriquez,
Harry Handoko Halim,
Yui Ogawa,
Yoshitaka Taniyasu,
Yuji Hamamoto,
Yoshitada Morikawa,
Yoshihiro Kobayashi
- We insert carbon nanotubes (CNT) as nanospacers to modulate the microstructure of multilayer stacking graphene. Nanospacers can increase interlayer distance and reduce interlayer interaction. The graphene/CNT stacking structure is experimentally fabricated and Raman spectroscopy verifies the reduction in interlayer interaction within the stacking structure. Thus, we study the microstructure of the stacked graphene and CNTs by molecular dynamics simulation to systematically investigate the effect of CNT insertion. The distribution distance, size, and arrangement of the CNT can modulate the interlayer distance. The graphene/CNT stacking structure exhibits two stable configurations: the upper-layer suspension and interlayer adsorption.
Latest version: v1
Publication date: Dec 14, 2023
Frederick Stein,
Jürg Hutter
- The Random-Phase approximation (RPA) provides an appealing framework for semi-local density functional theory. In its current formulation, it is cost-effective and has a better scaling behaviour compared to other wavefunction based correlation methods. To broaden the application field for RPA, it is necessary to have first order properties available. RPA nuclear gradients allow for structure optimizations and data sampling for machine learning applications. We report on an efficient implementation of RPA nuclear gradients for massively parallel computers. We apply the implementation to two polymorphs of the benzene crystal obtaining very good cohesive and relative energies. Different correction and extrapolation schemes are investigated for further improvement of the results and in order to estimate error bars.
Latest version: v2
Publication date: Dec 13, 2023
Alexandre A. Schoepfer,
Ruben Laplaza,
Matthew D. Wodrich,
Jerome Waser,
Clemence Corminboeuf
- Chiral ligands are important components in asymmetric homogeneous catalysis, but their synthesis and screening can be both time-consuming and resource-intensive. Data-driven approaches, in contrast to screening procedures based on intuition, have the potential to reduce the time and resources needed for reaction optimization by more rapidly identifying an ideal catalyst. These approaches, however, are often non-transferable and cannot be applied across different reactions. To overcome this drawback, we introduce a general featurization strategy for bidentate ligands that is coupled with an automated feature selection pipeline and Bayesian ridge regression to perform multivariate linear regression modeling. This approach, which is applicable to any reaction, incorporates electronic, steric, and topological features (rigidity/flexibility, branching, geometry, constitution) and is well-suited for early-stage ligand optimization. Using only small datasets, our workflow capably ...
Latest version: v1
Publication date: Dec 12, 2023
Ksenia R. Briling,
Yannick Calvino Alonso,
Alberto Fabrizio,
Clemence Corminboeuf
- Recently, we introduced a class of molecular representations for kernel-based regression methods — the spectrum of approximated Hamiltonian matrices (SPAᴴM) — that takes advantage of lightweight one-electron Hamiltonians traditionally used as an SCF initial guess. The original SPAᴴM variant is built from occupied-orbital energies (\ie, eigenvalues) and naturally contains all the information about nuclear charges, atomic positions, and symmetry requirements. Its advantages were demonstrated on datasets featuring a wide variation of charge and spin, for which traditional structure-based representations commonly fail. SPAᴴM(a,b), as introduced here, expands eigenvalue SPAᴴM into local and transferable representations. It relies upon one-electron density matrices to build fingerprints from atomic or bond density overlap contributions inspired from preceding state-of-the-art representations. The performance and efficiency of SPAᴴM(a,b) is assessed on the predictions for datasets of ...
Latest version: v1
Publication date: Dec 08, 2023
Yue Sun,
Fanhao Meng,
Changmin Lee,
Aljoscha Soll,
Hongrui Zhang,
Ramamoorthy Ramesh,
Jie Yao,
Zdeněk Sofer,
Joseph Orenstein
- Antiferromagnets are promising platforms for transduction and transmission of quantum information via magnons — the quanta of spin waves — and they offer advantages over ferromagnets in regard to dissipation, speed of response, and robustness to external fields. Recently, transduction was shown in a van der Waals antiferromagnets, where strong spin-exciton coupling enables readout of the amplitude and phase of coherent magnons by photons of visible light. This discovery shifts the focus of research to transmission, specifically to exploring the nonlocal interactions that enable magnon wave packets to propagate. Here we demonstrate that magnon propagation is mediated by the long-range dipole-dipole interaction. This coupling is an inevitable consequence of fundamental electrodynamics, and as such, will likely mediate the propagation of spin at long wavelengths in the entire class of van der Waals magnets currently under investigation. Successfully identifying the mechanism of spin ...
Latest version: v1
Publication date: Dec 08, 2023
Matthäus Siebenhofer,
Andreas Nenning,
Christoph Rameshan,
Peter Blaha,
Jürgen Fleig,
Markus Kubicek
- This dataset includes all data presented in the figures of the main manuscript: XPS work function changes, ab-initio calculated work functions, O2p band center shifts, Densities of state for LSC and PCO, i-PLD results for LSC, LSF, STF and PCO, Densities of state for adsorbed O2 on differently decorated PCO surfaces. In this work, we investigated surface dipole changes which were induced by modification of mixed conducting surfaces with binary oxides via pulsed laser deposition.
Latest version: v1
Publication date: Dec 08, 2023
Frédéric Célerse,
Matthew D. Wodrich,
Sergi Vela,
Simone Gallarati,
Raimon Fabregat,
Veronika Juraskova,
Clémence Corminboeuf
- Structurally and conformationally diverse databases are needed to train accurate neural networks or kernel-based potentials capable of exploring the complex free energy landscape of flexible functional organic molecules. Curating such databases for species beyond “simple” drug-like compounds or molecules comprised of well-defined building blocks (e.g., peptides) is challenging, as it requires thorough chemical space mapping and evaluation of both chemical and conformational diversity. Here, we introduce the OFF–ON (Organic Fragments From Organocatalysts that are Non-modular) database, a repository of 7,869 equilibrium and 67,457 non--equilibrium geometries of organic compounds and dimers aimed at describing conformationally flexible functional organic molecules, with an emphasis on photoswitchable organocatalysts. The relevance of this database is then demonstrated by training a Local Kernel Regression model on a low-cost semiempirical baseline and comparing it with a PBE0-D3 ...
Latest version: v1
Publication date: Dec 08, 2023
Binglun Yin,
Linhan Li,
Sophie Drescher,
Sascha Seils,
Shankha Nag,
Jens Freudenberger,
William Curtin
- AuNi is a classic long-studied fcc alloy combining a very “large” atom (Au) and a very “small” atom (Ni), and the large atomic size misfits suggest very high strengthening. Here, AuNi is used as a model alloy for the testing of new strengthening theories in random alloys that include the effects of both size misfits and solute–solute interactions. Experimentally, AuNi samples are fabricated, characterized, and tested, and show no segregation after annealing at 900 °C and a very high yield strength of 769 MPa. Theoretically, the main inputs to the theory (alloy lattice and elastic constants, solute misfit volumes, energy fluctuations associated with slip in the presence of solute–solute interactions) are extracted from experiments or computed using first-principles DFT. The parameter-free prediction of the yield strength is 809 MPa, in very good agreement with experiments. Solute–solute interactions enhance the strength only moderately (13%), demonstrating that the strengthening is ...
Latest version: v1
Publication date: Dec 01, 2023
Garu Gebreyesus,
Lorenzo Bastonero,
Michele Kotiuga,
Nicola Marzari,
Iurii Timrov
- We present a first-principles study of the low-temperature rhombohedral phase of BaTiO₃ using Hubbard-corrected density-functional theory. By employing density-functional perturbation theory, we compute the onsite Hubbard U for Ti(3d) states and the intersite Hubbard V between Ti(3d) and O(2p) states. We show that applying the onsite Hubbard U correction alone to Ti(3d) states proves detrimental, as it suppresses the Ti(3d)-O(2p) hybridization and drives the system towards a cubic phase. Conversely, when both onsite U and intersite V are considered, the localized character of the Ti(3d) states is maintained, while also preserving the Ti(3d)-O(2p) hybridization, restoring the rhombohedral phase of BaTiO₃. The generalized PBEsol+U+V functional yields good agreement with experimental results for the band gap and dielectric constant, while the optimized geometry is slightly less accurate compared to PBEsol. Zone-center phonon frequencies and Raman spectra are found to be significantly ...
Latest version: v1
Publication date: Nov 30, 2023
Zhengyuan Li,
Peng Wang,
Xiang Lyu,
Vamsi Krishna Reddy Kondapalli,
Shuting Xiang,
Juan D. Jimenez,
Lu Ma,
Takeshi Ito,
Tianyu Zhang,
Jithu Raj,
Yanbo Fang,
Yaocai Bai,
Jianlin Li,
Alexey Serov,
Vesselin Shanov,
Anatoly I. Frenkel,
Sanjaya D. Senanayake,
Yang Shize,
Thomas Senftle,
Jingjie Wu
- This dataset includes all the atomic coordinates of the optimized computational models from electronic structure calculations reported in the manuscript. In this work, we highlight that single-site noble metal dopants on the Cu surface can influence C–O bond dissociation in a key selectivity-determining intermediate (e.g., oxygen-bound *CH₂CHO), which in turn direct the post-C–C coupling pathways to ethylene versus ethanol. Combining theoretical and experimental analyses, we demonstrate that the favorability of C–O bond scission is controlled by the oxygen affinity of the metal dopant on the Cu catalyst. We find that the selectivity ratio of ethylene-to-ethanol displays a volcano relationship with respect to the oxygen binding strength on the doped surfaces.
Latest version: v1
Publication date: Nov 30, 2023
Xin Liu,
William Curtin
- Prismatic slip of the screw <a> dislocation in magnesium at temperatures ≳ 150 K is understood to be governed by double-cross-slip of the stable basal screw through the unstable prism screw and back to the basal screw, with the activation energy controlled by the formation energy of two basal-basal kinks. However, atomistic studies of the double-kink process predict activation energies roughly twice those derived experimentally. Here, a new mechanism of prism glide is proposed, analyzed theoretically, and demonstrated qualitatively and quantitatively via direct molecular dynamics (MD) simulations. The new mechanism is intrinsically 3d, and involves the nucleation of a single kink at the junction where a 3d prismatic dislocation loop transitions from the basal screw segment to non-screw prismatic character. The relevant kink energies are calculated using recently-developed Neural-Network Potentials (NNPs) for Mg that show good agreement versus DFT for basal and prism <a> ...
Latest version: v1
Publication date: Nov 30, 2023
Xin Liu,
William Curtin
- A theory for strengthening for multicomponent non-dilute alloys possessing short-range order (SRO) has recently been developed. The theory predicts that, in addition to a well-known athermal strengthening, there is a notable effect of SRO on the solute–dislocation interactions that can decrease or increase the strength relative to a random alloy. Here, carefully designed atomistic simulations in a model binary NbW alloy are used to demonstrate that alloy strength due to solute–dislocation interactions can be increased or decreased, depending on the SRO and consistent with theoretical predictions. Specifically, SRO is introduced using fictitious solute– solute interactions in an alloy system with very small true solute–solute interactions, and the Nudged Elastic Band (NEB) method is then used to compute the energy barriers for edge dislocation motion for various levels of SRO. Energy barriers, and hence alloy strengths, can be decreased when the Warren-Cowley SRO parameters are ...
Latest version: v1
Publication date: Nov 30, 2023
Oleksandr Pylypovskyi,
Sophie Weber,
Pavlo Makushko,
Igor Veremchuk,
Nicola Spaldin,
Denys Makarov
- Antiferromagnets are normally thought of as materials with compensated magnetic sublattices. This adds to their technological advantages but complicates readout of the antiferromagnetic state. We demonstrate theoretically the existence of a Dzyaloshinskii-Moriya interaction (DMI) which is determined by the magnetic symmetry classes of Cr₂O₃ surfaces with an in-plane magnetic easy axis. The DMI explains a previously predicted out-of-plane magnetization at the nominally compensated surfaces of chromia, leading to a surface-localized canted ferrimagnetism. This is in agreement with magnetotransport measurements and with density functional theory predictions which further allow us to quantify the strength of DMI. The temperature dependence of the transversal resistance for these planes shows distinct behavior in comparison with that of the Cr₂O₃ plane, which we attribute to the influence of DMI. Our work provides a framework to analyze surface-driven phenomena in antiferromagnets, ...
Latest version: v1
Publication date: Nov 29, 2023
Augustin Bussy,
Jürg Hutter
- Simulations of condensed matter systems at the hybrid density functional theory (DFT) level pose significant computational challenges. The elevated costs arise from the non-local nature of the Hartree-Fock exchange (HFX) in conjunction with the necessity to approach the thermodynamic limit (TDL). In this work, we address these issues with the development of a new efficient method for the calculation of HFX in periodic systems, employing k-point sampling. We rely on a local atom-specific resolution-of-the-identity scheme, the use of atom-centered Gaussian type orbitals (GTOs), and the truncation of the Coulomb interaction to limit computational complexity. Our real-space approach exhibits a scaling that is at worst linear with the number of k-points. Issues related to basis set diffuseness are effectively addressed through the auxiliary density matrix method (ADMM). We report the implementation in the CP2K software package, as well as accuracy and performance benchmarks. The ...
Latest version: v1
Publication date: Nov 29, 2023
Zhiqi Wang,
Yutong Gong,
Matthew L. Evans,
Yujing Yan,
Shiyao Wang,
Nanxi Miao,
Ruiheng Zheng,
Gian-Marco Rignanese,
Junjie Wang
- This study combines machine learning (ML) and high-throughput calculations to uncover new ternary electrides in the A₂BC₂ family of compounds with the P4/mbm space group. Starting from a library of 214 known A₂BC₂ phases, density-functional theory calculations were used to compute the maximum value of the electron localization function, indicating that 42 are potential electrides. A model was then trained on this dataset and used to predict the electride behaviour of 14,437 hypothetical compounds generated by structural prototyping. Then, the stability and electride features of the 1254 electride candidates predicted by the model were carefully checked by high-throughput calculations.
Latest version: v1
Publication date: Nov 28, 2023
Robin Hilgers,
Daniel Wortmann,
Stefan Blügel
- The uploaded data set contains setups of all 6660 possible combinations of up to three atomic layers of 3d transition metals on six different FCC noble-metal substrates. The substrates are modelled by five layers of Ag, Au, Pd, Pt, Rh or Ir in the (001) orientation. Nearly all structures (6282) have been relaxed, i.e. their ground state atomic configuration has been determined by density functional theory calculations. This has been achieved using a workflow implemented in the AiiDA-FLEUR package that first determines the substrate lattice constant and then relaxes the interlayer distances of the ad-layers using the forces calculated. All simulations have been performed using the FLAPW code FLEUR with the standard GGA-PBE exchange-correlation functional. A significant portion of these 3d thin films exhibits magnetic properties and thus could have applications in emerging technological fields such as e.g. spintronics. Therefore, the database also includes the magnetic properties of ...
Latest version: v1
Publication date: Nov 22, 2023
Aik Rui Tan,
Shingo Urata,
Samuel Goldman,
Johannes C. B. Dietschreit,
Rafael Gómez-Bombarelli
- Neural networks (NNs) often assign high confidence to their predictions, even for points far out-of-distribution, making uncertainty quantification (UQ) a challenge. When they are employed to model interatomic potentials in materials systems, this problem leads to unphysical structures that disrupt simulations, or to biased statistics and dynamics that do not reflect the true physics. Differentiable UQ techniques can find new informative data and drive active learning loops for robust potentials. However, a variety of UQ techniques, including newly developed ones, exist for atomistic simulations and there are no clear guidelines for which are most effective or suitable for a given case. In this work, we examine multiple UQ schemes for improving the robustness of NN interatomic potentials (NNIPs) through active learning. In particular, we compare incumbent ensemble-based methods against strategies that use single, deterministic NNs: mean-variance estimation, deep evidential ...
Latest version: v2
Publication date: Nov 21, 2023
Fu-li Sun,
Cun-biao Lin,
Wei Zhang,
Qing Chen,
Wen-xian Chen,
Xiao-nian Li,
Gui-lin Zhuang
- An excellent single-atomic photocatalyst, Ti@C₄N₃, is theoretically found to effectively convert CO₂ to C₂H₆ by density functional theory (DFT) calculations and non-adiabatic molecular dynamics (NAMD) simulations. The Ti@C₄N₃ photocatalyst has remarkable stability both thermally, chemically, and mechanically. Electronically, it has strong absorption properties, suitable band positions, and a long photogenerated electron lifetime, allowing photogenerated electrons to migrate to the surface. Notably, the high-valence active site effectively activates two CO₂ through dual activation: Under light irradiation, the weakly adsorbed CO₂ undergoes photo-induced activation by the photoelectron of conduction band minimum (CBM); without light, the high Lewis acidity of the Ti site induces CO₂ activation through back-donating π-bond. Contrast simulation results uncovered that dual activation of CO₂ is attributed to the thermal and photonic synergy. Furthermore, two activated CO₂ species under ...
Latest version: v1
Publication date: Nov 20, 2023
Geng Li,
Yingxiang Gao,
Daiyou Xie,
Leilei Zhu,
Dongjie Shi,
Shuming Zeng,
Wei Zhan,
Jun Chen,
Honghui Shang
- Raman spectra play an important role in characterizing two-dimensional materials, as they provide a direct link between the atomic structure and the spectral features. In this work, we present an automatic computational workflow for Raman spectra using all-electron density functional perturbation theory. Utilizing this workflow, we have successfully completed the Raman spectra calculation for 3504 different two-dimensional materials, with the resultant data saved in a data repository.
Latest version: v1
Publication date: Nov 16, 2023
Yuri Cho,
Ruben Laplaza,
Sergi Vela,
Clemence Corminboeuf
- Predicting the ground state spin of transition metal complexes is a challenging task. Previous attempts have been focused on specific regions of chemical space, whereas a more general automated approach is required to process crystallographic structures for high-throughput quantum chemistry computations. In this work, we developed a method to predict ground state spins of transition metal complexes. We started by constructing a dataset which contains 2,032 first row transition metal complexes taken from experimental crystal structures and their computed ground state spins. This dataset showed large chemical diversity in terms of metals, metal oxidation states, coordination geometries, and ligands. Then, we analyzed the trends between structural and electronic features of the complexes and their ground state spins, and put forward an empirical spin state assignment model. We also used simple descriptors to build a statistical model with 97% predictive accuracy across the board. ...
Latest version: v1
Publication date: Nov 15, 2023
Simone Gallarati,
Puck van Gerwen,
Ruben Laplaza,
Lucien Brey,
Alexander Makaveev,
Clemence Corminboeuf
- A catalyst possessing a broad substrate scope, in terms of both turnover and enantioselectivity, is sometimes called “general”. Despite their great utility in asymmetric synthesis, truly general catalysts are difficult or expensive to discover via traditional high-throughput screening and are, therefore, rare. Existing computational tools accelerate the evaluation of reaction conditions from a pre-defined set of experiments to identify the most general ones, but cannot generate entirely new catalysts with enhanced substrate breadth. For these reasons, we report an inverse design strategy based on the open-source genetic algorithm NaviCatGA and on the OSCAR database of organocatalysts to simultaneously probe the catalyst and substrate scope and optimize generality as primary target. We apply this strategy to the Pictet–Spengler condensation, for which we curate a database of 820 reactions, used to train statistical models of selectivity and activity. Starting from OSCAR, we define ...
Latest version: v2
Publication date: Nov 15, 2023
Bing Huang,
Anatole von Lilienfeld,
Jaron Krogel,
Anouar Benali
- In the past decade, quantum diffusion Monte Carlo (DMC) has been demonstrated to successfully predict the energetics and properties of a wide range of molecules and solids by numerically solving the electronic many-body Schrödinger equation. We show that when coupled with quantum machine learning (QML) based surrogate methods the computational burden can be alleviated such that QMC shows clear potential to undergird the formation of high quality descriptions across chemical space. We discuss three crucial approximations necessary to accomplish this: The fixed node approximation, universal and accurate references for chemical bond dissociation energies, and scalable minimal amons set based QML (AQML) models. Numerical evidence presented includes converged DMC results for over one thousand small organic molecules with up to 5 heavy atoms used as amons, and 50 medium sized organic molecules with 9 heavy atoms to validate the AQML predictions. Numerical evidence collected for 𝛥-AQML ...
Latest version: v2
Publication date: Nov 15, 2023
Giacomo Lorenzin,
Javier Fernandez Troncoso,
Manura Liyanage,
Aleksandr Druzhinin,
Lars Jeurgens,
Claudia Cancellieri,
Vladyslav Turlo
- Interface stress is a fundamental descriptor for interphase boundaries and is defined in strict relation to the interface energy. In nanomultilayered coatings with their intrinsically high interface density, the functional properties are generally dictated by the interface structure, which in turn is governed by the delicate interaction of residual interface and volume stresses in the coating system. In the present work, experimental estimations of the interface stress in Cu/W NMLs (with a variable residual stress state from tensile to compressive) were compared with corresponding theoretical values as calculated using DFT (adopting an incoherent bcc W{110}/fcc Cu{111} interface with variable in-plane strain). The Cu/W interface stress was experimentally tuned monotonically from positive to negative values by changing the residual stress in the W nanolayers by increasing the Ar pressure during the W deposition steps. Qualitative agreement between experiment and simulation was ...
Latest version: v1
Publication date: Nov 14, 2023
Raffaele Fiorentini,
Thomas Tarenzi,
Giovanni Mattiotti,
Raffaello Potestio
- Molecular dynamics simulations provide a wealth of data whose in-depth analysis can be computationally demanding and, sometimes, even unnecessary. Dimensionality reduction techniques are thus routinely employed to simplify and improve the interpretation of trajectories focusing on specific subsets of the system's atoms; a key issue, in this context, is to determine the optimal resolution level, i.e. the smallest number of atoms needed to preserve the largest information content from the full atomistic trajectory. Here, we introduce the protein optimal resolution identification method (PROPRE), an unsupervised approach built on information theory principles that determines the smallest number of atoms that need to be retained to attain a synthetic yet informative description of a protein. By applying the method to a protein dataset and two particular case studies, we show that this number is typically between 1.5 and 2 times the number of residues in a protein; nonetheless, the ...
Latest version: v1
Publication date: Nov 13, 2023
Eric Bousquet,
Eddy Lelièvre-Berna,
Navid Qureshi,
Jian-Rui Soh,
Nicola Ann Spaldin,
Andrea Urru,
Xanthe Henderike Verbeek,
Sophie Francis Weber
- We establish the sign of the linear magnetoelectric (ME) coefficient, α, in chromia, Cr₂O₃. Cr₂O₃ is the prototypical linear ME material, in which an electric (magnetic) field induces a linearly proportional magnetization (polarization), and a single magnetic domain can be selected by annealing in combined magnetic (H) and electric (E) fields. Opposite antiferromagnetic domains have opposite ME responses, and which antiferromagnetic domain corresponds to which sign of response has previously been unclear. We use density functional theory (DFT) to calculate the magnetic response of a single antiferromagnetic domain of Cr₂O₃ to an applied in-plane electric field at 0 K. We find that the domain with nearest neighbor magnetic moments oriented away from (towards) each other has a negative (positive) in-plane ME coefficient, α⊥, at 0 K. We show that this sign is consistent with all other DFT calculations in the literature that specified the domain orientation, independent of the choice ...
Latest version: v1
Publication date: Nov 13, 2023
M. dos Santos Dias,
N. Biniskos,
F. J. dos Santos,
K. Schmalzl,
J. Persson,
F. Bourdarot,
N. Marzari,
S. Blügel,
T. Brückel,
S. Lounis
- The phase of the quantum-mechanical wave function can encode a topological structure with wide-ranging physical consequences, such as anomalous transport effects and the existence of edge states robust against perturbations. While this has been exhaustively demonstrated for electrons, properties associated with the elementary quasiparticles in magnetic materials are still underexplored. Here, we show theoretically and via inelastic neutron scattering experiments that the bulk ferromagnet Mn₅Ge₃ hosts gapped topological Dirac magnons. Although inversion symmetry prohibits a net Dzyaloshinskii-Moriya interaction in the unit cell, it is locally allowed and is responsible for the gap opening in the magnon spectrum. This gap is predicted and experimentally verified to close by rotating the magnetization away from the c-axis. Hence, Mn₅Ge₃ is the first realization of a gapped Dirac magnon material in three dimensions. Its tunability by chemical doping or by thin film nanostructuring ...
Latest version: v2
Publication date: Nov 10, 2023
Soleil Chapman,
Innis Michael,
Walter Malone
- We present a large dataset of density functional theory calculations of thiophene (C4H4S) adsorbed on metallic and bimetallic (100) surfaces performed in Quantum Espresso. In total 1131 different surfaces were explored resulting in 2235 total calculations. Slabs were built from 37 different possible elements in the stoichiometry of A3B, Ll2 structures. The 37 single element slabs, A1 structures, were included as well. Slabs were cleaved in the (100) direction. Two hollow adsorption sites were chosen to be explored over bimetallic surfaces and one hollow configuration for the single metal surfaces. Bader charge analysis files are also presented.
Latest version: v1
Publication date: Nov 09, 2023
Siqi Wang,
Tongqi Wen,
Jian Han,
David Srolovitz
- The α/β interface is central to the microstructure and mechanical properties of titanium alloys. We investigate the structure, thermodynamics and migration of the coherent and semicoherent Ti α/β interfaces as a function of temperature and misfit strain via molecular dynamics (MD) simulations, thermodynamic integration and an accurate, DFT-trained Deep Potential. The structure of an equilibrium semicoherent interface consists of an array of steps, an array of misfit dislocations, and coherent terraces. Analysis determines the dislocation and step (disconnection) array structure and habit plane. The MD simulations show the detailed interface morphology dictated by intersecting disconnection arrays. The steps are shown to facilitate α/β interface migration, while the misfit dislocations lead to interface drag; the drag mechanism is different depending on the direction of interface migration. These results are used to predict the nature of α phase nucleation on cooling through the α-β phase transition.
Latest version: v1
Publication date: Nov 07, 2023
Robin Hilgers,
Daniel Wortmann,
Stefan Blügel
- The provided AiiDA database contains magnetic electronic structure calculations from a selection of full (L2₁) and inverse (XA) Heusler alloys. The examined crystal structures were taken from the Materials Project database. The data was obtained to examine the spin-polarization of the density of states amongst different compounds. The FLAPW code FLEUR has been combined with the GGA-based PBE functional to compute the structures. Spin-orbit interaction has been considered in second variation within the presented calculations.
Complete list of included Heusler compounds:
– L2₁: Co₂CrSb, Co₂GeCr, Co₂HfAl, Co₂HfGa, Co₂HfIn, Co₂ScGe, Co₂SnNb, Co₂VZn, Co₂ZnGe, Co₂ZnNb, Co₂ZnTa, Co₂ZrGa, Cu₂FeSn, Cu₂MnSb, Cu₂MnSn, Fe₂CoGa, Fe₂CoGe, Fe₂CoSi, Fe₂CrGa, Fe₂CrSi, Fe₂CrSi, Fe₂CrSn, Fe₂CrSn, Fe₂TaGe, Fe₂TiGa, Fe₂TiIn, FeMn₂P, Ir₂FeGa, Ir₂TcTl, Mn₂CrSi, Mn₂RuSi, Mn₂TaGe, Mn₂VIn, Mn₂WGa, Ni₂FeGa, Ni₂MnSb, Ni₂MnSi, Ni₂MnSn, Rh₂FeGa, Rh₂FeIn, Rh₂FeSn, Rh2MnSi, Rh2MnSn, Rh2TiMn, Rh2ZnFe, Ru2FeGe, ...
Latest version: v1
Publication date: Nov 03, 2023
Daniele Ongari,
Miriam J. Pougin,
Aliaksandr V. Yakutovich,
Leopold Talirz,
Berend Smit
- We present a workflow that traces the path from the bulk structure of a crystalline material to assessing its performance in carbon capture from coal’s postcombustion flue gases. This workflow is applied to a database of 324 covalent−organic frameworks (COFs) reported in the literature, to characterize their CO2 adsorption properties using the following steps:
(1) optimization of the crystal structure (atomic positions and unit cell) using density functional theory,
(2) fitting atomic point charges based on the electron density,
(3) characterizing the pore geometry of the structures before and after optimization,
(4) computing carbon dioxide and nitrogen isotherms using grand canonical Monte Carlo simulations with an empirical interaction potential, and finally,
(5) assessing the CO2 parasitic energy via process modeling.
The full workflow has been encoded in the Automated Interactive Infrastructure and Database for Computational Science (AiiDA). Both the workflow and the ...
Latest version: v10
Publication date: Nov 02, 2023
Tiago F. T. Cerqueira,
Antonio Sanna,
Miguel A. L. Marques
- We perform a large scale study of conventional superconducting materials using a machine-learning accelerated high-throughput workflow. We start by creating a comprehensive dataset of around 7000 electron-phonon calculations performed with reasonable convergence parameters. This dataset is then used to train a robust machine learning model capable of predicting the electron-phonon and superconducting properties based on structural, compositional, and electronic ground-state properties. Using this machine, we evaluate the transition temperature (Tc) of approximately 200000 metallic compounds, all of which on the convex hull of thermodynamic stability (or close to it) to maximize the probability of synthesizability. Compounds predicted to have Tc values exceeding 5 K are further validated using density-functional perturbation theory. As a result, we identify 541 compounds with Tc values surpassing 10 K, encompassing a variety of crystal structures ...
Latest version: v1
Publication date: Oct 30, 2023
Enrico Drigo,
Maria Grazia Izzo,
Stefano Baroni
- We present a method, based on the classical Green-Kubo theory of linear response, to compute the heat conductivity of extended systems, leveraging energy-density, rather than energy-current, fluctuations, thus avoiding the need to devise an analytical expression for the macroscopic energy flux. The implementation of this method requires the evaluation of the long-wavelength and low-frequency limits of a suitably defined correlation function, which we perform using a combination of recently-introduced cepstral-analysis and Bayesian extrapolation techniques. Our methodology is demonstrated against standard current-based Green-Kubo results for liquid argon and water, and solid amorphous Silica, and compared with a recently proposed similar technique, which utilizes mass-density, instead of energy-density, fluctuations.
Latest version: v1
Publication date: Oct 26, 2023
Simon Gelin,
Nicole E. Kirchner-Hall,
Rowan R. Katzbaer,
Monica J. Theibault,
Yihuang Xiong,
Wayne Zhao,
Mohammed M. Khan,
Eric Andrewlavage,
Paul Orbe,
Steven M. Baksa,
Matteo Cococcioni,
Iurii Timrov,
Quinn Campbell,
Héctor Abruña,
Raymond E. Schaak,
Ismaila Dabo
- Oxides containing metals or semimetals from the p-block of the periodic table, e.g., indium oxide or antimony oxide, are of interest as transparent conductors and light absorbers for solar energy conversion due to the tunability of their electronic conductivity and optical absorption. Comparatively, these oxides have found limited applications in solar-to-hydrogen photocatalysis primarily due to their high electronegativity, which impedes electron transfer for converting protons into hydrogen. We have shown recently that inserting s-block metal cations into p-block oxides is effective at lowering electronegativities while affording further control of band gaps. Here, we explain the origins of this dual tunability by demonstrating the mediator role of s-block metal cations in modulating orbital hybridization while not contributing to frontier electronic states. From this result, we carry out a comprehensive computational study of 109 ternary oxides of s- and p-block metal elements ...
Latest version: v1
Publication date: Oct 23, 2023
Kalyan Biswas,
Diego Soler,
Shantanu Mishra,
Qiang Chen,
Xuelin Yao,
Ana Sánchez-Grande,
Kristjan Eimre,
Pingo Mutombo,
Cristina Martín-Fuentes,
Koen Lauwaet,
José M. Gallego,
Pascal Ruffieux,
Carlo A. Pignedoli,
Klaus Müllen,
Rodolfo Miranda,
José I. Urgel,
Akimitsu Narita,
Roman Fasel,
Pavel Jelínek,
David Écija
- The design of open-shell carbon-based nanomaterials is at the vanguard of materials science, steered by their beneficial magnetic properties like weaker spin–orbit coupling than that of transition metal atoms and larger spin delocalization, which are of potential relevance for future spintronics and quantum technologies. A key parameter in magnetic materials is the magnetic exchange coupling (MEC) between unpaired spins, which should be large enough to allow device operation at practical temperatures. In a recent work, we theoretically and experimentally explore three distinct families of nanographenes (NGs) (A, B, and C) featuring majority zigzag peripheries. Through many-body calculations, we identify a transition from a closed-shell ground state to an open-shell ground state upon an increase of the molecular size. Our predictions indicate that the largest MEC for open-shell NGs occurs in proximity to the transition between closed-shell and open-shell states. Such predictions ...
Latest version: v1
Publication date: Oct 17, 2023
Jinzhen Huang,
Camelia Nicoleta Borca,
Thomas Huthwelker,
Nur Sena Yüzbasi,
Thomas J. Schmidt,
Emiliana Fabbri
- Co-based catalysts are promising candidates to replace the Ir/Ru-based oxides for the oxygen evolution reaction (OER) in an acidic environment. However, both the reaction mechanism and the active species in an acidic environment remain unclear. In this study, by combining surface-sensitive soft X-ray adsorption spectroscopy (sXAS) characterization with electrochemical analysis, we unveil the truly active Co species for acidic OER. Surfaces composed of only high-spin CoII are found to be not active due to their unfavorable deprotonation to form CoIII-OH species. In contrast, we show that the presence of low-spin CoIII is essential to promote surface reconstruction and catalysis of OER. The correlation between OER activity and Co oxidation/spin state represents a breakthrough in the structure-activity relationship of Co-based catalysts for acidic OER, which interestingly does not hold in the alkaline and neutral environments. These findings not only ...
Latest version: v1
Publication date: Oct 17, 2023
Jinzhen Huang,
Natasha Hales,
Adam H. Clark,
Nur Sena Yüzbasi,
Camelia Nicoleta Borca,
Thomas Huthwelker,
Thomas J. Schmidt,
Emiliana Fabbri
- CeO₂ greatly enhances the electrocatalytic oxygen evolution reaction (OER) activity of CoOx, though the enhancement mechanism beyond this synergy is yet to be understood. Here, operando hard X-ray adsorption spectroscopy (hXAS) is applied to monitor the Co K edge and Ce L₃ edge in CoOx/CeO₂ to shed light on the evolution of the Co and Ce oxidation states during OER. In addition, ex situ soft XAS (sXAS) characterizations provide information on the irreversible surface-specific transformations of the Co L₃ edge as well as of the O K edge. Combining the operando and ex situ spectroscopic characterizations with comprehensive electrochemical analyses, we confirm CeO₂ is not the active center for the OER. However, coupling CeO₂ with CoOx introduces significant modifications in the Co and O species at the CoOx surface and alters the flat band potential (Efb), leading to more favorable Co oxidation state transformations during OER and possibly ...
Latest version: v1
Publication date: Oct 17, 2023
Flavio Giorgianni,
Björn Wehinger,
Stephan Allenspach,
Nicola Colonna,
Carlo Vicario,
Pascal Puphal,
Ekaterina Pomjakushina,
Bruce Normand,
Christian Rüegg
- Ideal magnetic frustration forms the basis for the emergence of exotic quantum spin states that are entirely nonmagnetic. Such singlet spin states are the defining feature of the Shastry-Sutherland model, and of its faithful materials realization in the quantum antiferromagnet SrCu₂(BO₃)₂. To address these states on ultrafast timescales, despite their lack of any microscopic order parameter, we introduce a nonlinear magnetophononic mechanism to alter the quantum spin dynamics by driving multiple optical phonon modes coherently and simultaneously. We apply intense terahertz pulses to create a nonequilibrium modulation of the magnetic interactions that breaks the ideal frustration of SrCu₂(BO₃)₂, such that previously forbidden physics can be driven in a coherent manner. Specifically, this driving populates a purely magnetic excitation, the singlet branch of the two-triplon bound state, by resonance with the difference frequency of two pumped phonons. Our results demonstrate how ...
Latest version: v2
Publication date: Oct 17, 2023
Amogh Kinikar,
Xiushang Xu,
Marco Di Giovannantonio,
Oliver Gröning,
Kristjan Eimre,
Carlo Antonio Pignedoli,
Klaus Müllen,
Akimitsu Narita,
Pascal Ruffieux,
Roman Fasel
- In this record we provide the data to support our recent finding on the synthesis of edge-extended zigzag graphene nanoribbons. Graphene nanoribbons (GNRs) have gained significant attention in nanoelectronics due to their potential for precise tuning of electronic properties through variations in edge structure and ribbon width. However, the synthesis of GNRs with highly sought‐after zigzag edges (ZGNRs), critical for spintronics and quantum information technologies, remains challenging. In the manuscript where the data presented here is discussed, a design motif for synthesizing a novel class of GNRs termed edge‐extended ZGNRs is presented. This motif enables the controlled incorporation of edge extensions along the zigzag edges at regular intervals. The synthesis of a specific GNR instance—a 3‐zigzag‐rows‐wide ZGNR—with bisanthene units fused to the zigzag edges on alternating sides of the ribbon axis is successfully demonstrated. The resulting edge‐extended 3‐ZGNR is ...
Latest version: v1
Publication date: Oct 13, 2023
Tenghua Gao,
Philipp Rüßmann,
Qianwen Wang,
Hiroki Hayashi,
Dongwook Go,
Song Zhang,
Takashi Harumoto,
Rong Tu,
Lianmeng Zhang,
Yuriy Mokrousov,
Ji Shi,
Kazuya Ando
- Spintronics applications for high-density non-volatile memories require simultaneous optimization of the perpendicular magnetic anisotropy (PMA) and current-induced magnetization switching. These properties determine, respectively, the thermal stability of a ferromagnetic memory cell and a low operation power consumption, which are mutually incompatible with the spin transfer torque as the driving force for the switching. Here, we demonstrate a strategy of alloy engineering to overcome this obstacle by using electrically induced orbital currents instead of spin currents. A non-equilibrium orbital density generated in paramagnetic γ-FeMn flows into CoPt coupled to the magnetization through spin-orbit interaction, ultimately creating an orbital torque. Controlling the atomic arrangement of Pt and Co by structural phase transition, we show that the propagation length of the transferred angular momentum can be modified concurrently with the PMA strength. We find a strong correlation ...
Latest version: v1
Publication date: Oct 13, 2023
Zhishuo Huang,
Munirah D. Albaqami,
Tohru Sato,
Naoya Iwahara,
Liviu F. Chibotaru
- Compared to isolated C₆₀³⁻ ions, characterized by a three-dimensional equipotential trough at the bottom of the lowest adiabatic potential energy surface (APES), the Jahn-Teller (JT) effect in cubic fullerides is additionally influenced by the interaction of JT distortions at C₆₀ sites with vibrational modes of the lattice. This leads to modification of JT stabilization energy and to the warping of the trough at each fullerene site, as well as to the interaction of JT distortions at different sites. Here we investigate these effects in three fcc fullerides with A = K, Rb, Cs and in Cs₃C₆₀ with bcc (A15) structure. DFT calculations of orbital vibronic coupling constants at C₆₀ sites and of phonon spectra have been done for fully ordered lattices (1 C₆₀/u.c.). Based on them the elastic response function for local JT distortions has been evaluated and the lowest APES investigated. To this end an expression for the latter as a function of trough coordinates of all sites has been ...
Latest version: v1
Publication date: Oct 10, 2023
Xanthe Henderike Verbeek,
Andrea Urru,
Nicola Ann Spaldin
- We present ab initio calculations of hidden magnetoelectric multipolar order in Cr₂O₃ and its iron-based analogue, α-Fe₂O₃. We show the presence of hidden antiferroically-ordered magnetoelectric multipoles in both the prototypical magnetoelectric material Cr₂O₃, and centrosymmetric α-Fe₂O₃, which has the same crystal structure as Cr₂O₃, but a different magnetic dipolar ordering. In turn, we predict anti-magnetoelectric effects, in which local magnetic dipole moments are induced in opposite directions under the application of an external electric field, to create an additional antiferromagnetic ordering. We confirm the predicted induced moments using first-principles calculations. Our results demonstrate the existence of hidden magnetoelectric multipoles leading to local linear magnetoelectric responses even in centrosymmetric materials, where a net bulk linear magnetoelectric effect is forbidden by symmetry. This archive contains input files and some output files necessary for ...
Latest version: v1
Publication date: Oct 05, 2023
Kevin K. Huguenin-Dumittan,
Philip Loche,
Haoran Ni,
Michele Ceriotti
- One essential ingredient in many machine learning (ML) based methods for atomistic modeling of materials and molecules is the use of locality. While allowing better system-size scaling, this systematically neglects long-range (LR) effects, such as electrostatics or dispersion interaction. We present an extension of the long distance equivariant (LODE) framework that can handle diverse LR interactions in a consistent way, and seamlessly integrates with preexisting methods by building new sets of atom centered features. We provide a direct physical interpretation of these using the multipole expansion, which allows for simpler and more efficient implementations. The framework is applied to simple toy systems as proof of concept, and a heterogeneous set of molecular dimers to push the method to its limits. By generalizing LODE to arbitrary asymptotic behaviors, we provide a coherent approach to treat arbitrary two- and many-body non-bonded interactions in the data-driven modeling of matter.
Latest version: v1
Publication date: Oct 03, 2023
Pascal Thomas Salzbrenner,
Se Hun Joo,
Lewis J Conway,
Peter I C Cooke,
Bonan Zhu,
Milosz P Matraszek,
William Charles Witt,
Chris J Pickard
- Machine-learned interatomic potentials are fast becoming an indispensable tool in computational materials science. One approach is the ephemeral data-derived potential (EDDP), which was designed to accelerate atomistic structure prediction. The EDDP is simple and cost-efficient. It relies on training data generated in small unit cells and is fit using a lightweight neural network, leading to smooth interactions which exhibit the robust transferability essential for structure prediction. Here, we present a variety of applications of EDDPs, enabled by recent developments of the open-source EDDP software. New features include interfaces to phonon and molecular dynamics codes, as well as deployment of the ensemble deviation for estimating the confidence in EDDP predictions. Through case studies ranging from elemental carbon and lead to the binary scandium hydride and the ternary zinc cyanide, we demonstrate that EDDPs can be trained to cover wide ranges of pressures and ...
Latest version: v1
Publication date: Sep 28, 2023
Anees Pazhedath,
Lorenzo Bastonero,
Nicola Marzari,
Michele Simoncelli
- Alloys based on lanthanum phosphate (LaPO₄) are often employed as thermal barrier coatings, due to their low thermal conductivity and structural stability over a wide temperature range. To enhance the thermal-insulation performance of these alloys, it is essential to comprehensively understand the fundamental physics governing their heat conduction. Here, we employ the Wigner formulation of thermal transport in conjunction with first-principles calculations to elucidate how the interplay between anharmonicity and compositional disorder determines the thermal properties of La1-xGdxPO₄ alloys, and discuss the fundamental physics underlying the emergence and coexistence of particle-like and wave-like heat-transport mechanisms. Our predictions for microscopic vibrational properties (temperature-dependent Raman spectrum) and for macroscopic thermal conductivity are validated against experiments. Finally, we leverage these findings to devise strategies to optimize the performance of thermal barrier coatings.
Latest version: v1
Publication date: Sep 27, 2023
Norma Rivano,
Nicola Marzari,
Thibault Sohier
- Dimensionality provides a clear fingerprint on the dispersion of infrared-active, polar-optical phonons. For these phonons, the local dipoles parametrized by the Born effective charges drive the LO-TO splitting of bulk materials; this splitting actually breaks down in two-dimensional materials. Here, we develop the theory for one-dimensional (1D) systems -nanowires, nanotubes, and atomic and polymeric chains. Combining an analytical model with the implementation of density-functional perturbation theory in 1D boundary conditions, we show that the dielectric splitting in the dispersion relations collapses as x²log(x) at the zone center. The dielectric properties and the radius of the 1D materials are linked by the present work to these red shifts, opening infrared and Raman characterization avenues.
Latest version: v1
Publication date: Sep 27, 2023
