Oliviero Cannelli¹, Julia Wiktor², Nicola Colonna^3,4*, Ludmila Leroy^1,5, Michele Puppin¹, Camila Bacellar⁶, Ilia Sadykov⁷, Franziska Krieg^8,9, Grigory Smolentsev¹⁰, Maksym V. Kovalenko^8,9, Alfredo Pasquarello¹¹, Majed Chergui¹, Giulia F. Mancini¹²

1 Laboratory of Ultrafast Spectroscopy (LSU) and Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland

2 Department of Physics, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden

3 Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland

4 National Centre for Computational Design and Discovery of Novel Materials (MARVEL), Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland

5 LabCri, Departamento de Física, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte, Brazil

6 Laboratory for Femtochemistry, Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland

7 Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland

8 Institute of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, CH-8093 Zürich, Switzerland

9 Laboratory for Thin Films and Photovoltaics, Empa-Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf, Switzerland

10 Laboratory for Catalysis and Sustainable Chemistry, Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland

11 Chaire de Simulation à l’Echelle Atomique (CSEA), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland

12 Laboratory for Ultrafast X-ray and Electron Microscopy (LUXEM), Department of Physics, University of Pavia, I-27100 Pavia, Italy

* Corresponding authors emails: nicola.colonna@psi.ch

DOI10.24435/materialscloud:vg-1m [version v1]

Publication date: Sep 14, 2023

How to cite this record

Oliviero Cannelli, Julia Wiktor, Nicola Colonna, Ludmila Leroy, Michele Puppin, Camila Bacellar, Ilia Sadykov, Franziska Krieg, Grigory Smolentsev, Maksym V. Kovalenko, Alfredo Pasquarello, Majed Chergui, Giulia F. Mancini, Atomic-level description of thermal fluctuations in inorganic lead halide perovskites, Materials Cloud Archive 2023.139 (2023), https://doi.org/10.24435/materialscloud:vg-1m

Description

The potential of lead-halide perovskites for realistic applications is currently hindered by their limited long-term stability under functional activation. While the role of lattice flexibility in the thermal response of perovskites has become increasingly evident, the description of thermally-induced distortions is still unclear. In this work, we provide a unified picture of thermal activation in CsPbBr₃ across length scales, showing that lattice symmetry does not increase at high temperatures. We combine temperature-dependent XRD, Br K-edge XANES, ab initio MD simulations, and calculations of the XANES spectra by first-principles, accounting for both thermal fluctuations and core hole final state effects. We find that the octahedral tilting of the Pb-Br inorganic framework statistically adopts multiple local configurations over time - in the short-range. In turn, the stochastic nature of the local thermal fluctuations uplifts the longer-range periodic octahedral tilting characterizing the low temperature structure, with the statistical mean of the local configurations resulting in a cubic-like time-averaged lattice. These observations can be rationalized in terms of displacive thermal phase transitions through the soft mode model, in which the phonon anharmonicity of the flexible inorganic framework causes the excess free energy surface to change as a function of temperature. Our work demonstrates that the effect of thermal dynamics on the XANES spectra can be effectively described for largely anharmonic systems, provided ab initio MD simulations are performed to determine the dynamically fluctuating structures, and core hole final state effects are included in order to retrieve an accurate XANES line shape. Moreover, it shows that the soft mode model, previously invoked to describe displacive thermal phase transitions in oxide perovskites, carries a more general validity.

Materials Cloud sections using this data

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File name	Size	Description
README.txt MD5md5:2c4d520015140d4d77cbe1a25d47b36e	6.1 KiB	Readme file containing the information about the structure of archive dataset.tar.gz and the description of files and data inside the archive dataset.tar.gz
dataset.tar.gz MD5md5:9dfd43e316dfb9a91bb84806df8ec883	76.6 MiB	Archive containing the raw data, inputs/outputs and scripts to reproduce the results and the figures reported in the publication

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External references

Keywords

MARVEL halide perovskites XAS simulation molecular dynamics simulation