Luigi Giacomazzi^1,2*, Nikita S. Shcheblanov^3,4*, Mikhail E. Povarnitsyn⁵, Yanbo Li⁶, Andraž Mavrič², Barbara Zupančič⁷, Jože Grdadolnik⁷, Alfredo Pasquarello^8*

1 Institute of Materials (IOM), National Research Council of Italy (CNR), c/o SISSA Via Bonomea 265, IT-34136 Trieste, Italy

2 Materials Research Laboratory, University of Nova Gorica, Vipavska 11c, SI-5270 Ajdovščina, Slovenia

3 Navier, UMR 8205, Ecole des Ponts ParisTech, Univ. Gustave Eiffel, CNRS, Marne-la-Vallée, France

4 MSME, UMR 8208, Univ. Gustave Eiffel, CNRS, Univ. Paris-Est Créteil, Marne-la-Vallée, France

5 Joint Institute for High Temperatures, RAS, 13 Building 2 Izhorskaya Street, Moscow 125412, Russia

6 Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu, 610054 China

7 Laboratory for Molecular Structural Dynamics, Theory Department, National Institute of Chemistry, 1000 Ljubljana, Slovenia

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

* Corresponding authors emails: giacomazzi@iom.cnr.it, n.s.shcheblanov@gmail.com, alfredo.pasquarello@epfl.ch

DOI10.24435/materialscloud:mc-wf [version v1]

Publication date: Sep 14, 2023

How to cite this record

Luigi Giacomazzi, Nikita S. Shcheblanov, Mikhail E. Povarnitsyn, Yanbo Li, Andraž Mavrič, Barbara Zupančič, Jože Grdadolnik, Alfredo Pasquarello, Infrared spectra in amorphous alumina, Materials Cloud Archive 2023.140 (2023), https://doi.org/10.24435/materialscloud:mc-wf

Description

We present a combined study based on experimental measurements of infrared (IR) dielectric function and first-principles calculations of IR spectra and vibrational density of states (VDOS) of amorphous alumina (am-Al₂O₃). In particular, we show that the main features of the imaginary part of the dielectric function ε₂(ω) at ~380 and 630 cm-¹ are related to the motions of threefold coordinated oxygen atoms, which are the vast majority of oxygen atoms in am-Al₂O₃. Our analysis (involving three model structures) provides an alternative point of view with respect to an earlier suggested assignment of the vibrational modes, which relates them to the stretching and bending vibrational modes of AlOₙ (n = 4, 5, and 6) polyhedra. Our assignment is based on the additive decomposition of the VDOS and ε₂(ω) spectra, which shows that: (i) the band at ~380 cm-¹ features oxygen motions occurring in a direction normal to the plane defined by the three nearest-neighbor aluminum atoms, i.e. out-of-plane motions of oxygen atoms; (ii) Al-O stretching vibrations (i.e. in-plane motions of oxygen atoms) appear at frequencies above ~500 cm-¹, which characterize the vibrational modes underlying the band at ~630 cm-¹.

Materials Cloud sections using this data

Files

File name	Size	Description
Model_I_Al2O3.xyz MD5md5:bd2d23f0205c8007d6a4d81c0944b51a	7.7 KiB	The atomic structure of the bulk amorphous alumina model labelled as "model I" in Phys. Rev. Mater. 7, 045604 (2023). The model was originally generated in Colleoni et al. Appl. Phys. Lett. 107, 211601 (2015) via Born-Oppenheimer molecular dynamics simulations following a quench-from-the-melt approach. Atomic positions were further refined through a first-principle relaxation (DFT-PBE) in Phys. Rev. Mater. 7, 045604 (2023). This model contains 160 atoms.
Model_II_Al2O3.xyz MD5md5:82557ed1798b5c14488d07fb6af2ed03	5.8 KiB	The atomic structure of the bulk amorphous alumina model labelled as "model II" in Phys. Rev. Mater. 7, 045604 (2023). The model was originally generated (model G) in Momida et al. Phys. Rev. B 73, 054108 (2006) by means of classical molecular dynamics through a quench-from-the-melt procedure. Atomic positions were further refined through a first-principle relaxation (DFT-PBE) in Phys. Rev. Mater. 7, 045604 (2023). This model contains 120 atoms.
Model_III_Al2O3.xyz MD5md5:8a6e9dd2cb8932cf68be24651a405cc5	7.9 KiB	The atomic structure of the bulk amorphous alumina model labelled as "model III" in Phys. Rev. Mater. 7, 045604 (2023). The model was originally generated (model H) in Momida et al Phys. Rev. B 73, 054108 (2006) by means of classical molecular dynamics through a quench-from-the-melt procedure. Atomic positions were further refined through a first-principle relaxation (DFT-PBE) in Phys. Rev. Mater. 7, 045604 (2023). This model contains 120 atoms.
readme.txt MD5md5:03c37c90c8111f3b50ac8480b57c3d58	1.8 KiB	full description of the atomic structures of the am-Al₂O₃ models including lattice parameters

License

Files and data are licensed under the terms of the following license: Creative Commons Attribution 4.0 International.
Metadata, except for email addresses, are licensed under the Creative Commons Attribution Share-Alike 4.0 International license.

External references

Keywords

DFT amorphous Al2O3 infrared VDOS