| Title: | Infrared spectra in amorphous alumina: A combined ab initio and experimental study |
|---|
| Authors: | ID Giacomazzi, Luigi, Institute of Materials (IOM), National Research Council of Italy (CNR), c/o SISSA Via Bonomea 265, IT-34136 Trieste, Italy and Materials Research Laboratory, University of Nova Gorica, Vipavska 11c, SI-5270 Ajdovščina, Slovenia (Author)
ID Shcheblanov, Nikita S., Navier, UMR 8205, Ecole des Ponts ParisTech, Université Gustave Eiffel, CNRS, Marne-la-Vallée, France and MSME, UMR 8208, Université Gustave Eiffel, CNRS, Université Paris-Est Créteil, Marne-la-Vallée, France (Author)
ID Povarnitsyn, Mikhail E., Joint Institute for High Temperatures, RAS, 13 Building 2, Izhorskaya Street, Moscow 125412, Russia (Author)
ID Li, Yanbo, Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 610054, China (Author)
ID Mavrič, Andraž, Materials Research Laboratory, University of Nova Gorica, Vipavska 11c, SI-5270 Ajdovščina, Slovenia (Author)
ID Zupančič, Barbara, Laboratory for Molecular Structural Dynamics, Theory Department, National Institute of Chemistry, 1000 Ljubljana, Slovenia (Author)
ID Grdadolnik, Jože, Laboratory for Molecular Structural Dynamics, Theory Department, National Institute of Chemistry, 1000 Ljubljana, Slovenia (Author)
ID Pasquarello, Alfredo, Chaire de Simulation à l'Echelle Atomique (CSEA), Ecole Fédérale Polytechnique de Lausanne (EPFL), CH-1015 Lausanne, Switzerland (Author) |
|---|
| Files: |  https://arxiv.org/abs/2304.14090
|
|---|
| Language: | English |
|---|
| Work type: | Not categorized |
|---|
| Typology: | 1.01 - Original Scientific Article |
|---|
| Organization: | UNG - University of Nova Gorica
|
|---|
| Abstract: | We present a combined study based on the experimental measurements of an infrared (IR) dielectric function and first-principles calculations of IR spectra and the 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 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 ∼380cm−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 ∼500cm−1, which characterize the vibrational modes underlying the band at ∼630cm−1. Aluminum and fourfold-coordinated oxygen atoms contribute uniformly to the VDOS and ε2(ω) spectra in the frequency region ∼350–650 cm−1 without causing specific features. Our numerical results are in good agreement with the previous and presently obtained experimental data on the IR dielectric function of am−Al2O3 films. Finally, we show that the IR spectrum can be modeled successfully by assuming isotropic Born charges for aluminum atoms and fourfold-coordinated oxygen atoms, while requiring the use of three parameters, defined in a local reference frame, for the anisotropic Born charges of threefold-coordinated oxygen atoms. |
|---|
| Keywords: | Dielectric properties, Microstructure, Amorphous materials, Density functional calculations, Infrared techniques, aluminium oxide |
|---|
| Article version: | Publisher's version of article |
|---|
| Year of publishing: | 2023 |
|---|
| Number of pages: | 14 |
|---|
| Numbering: | 2023, 7 |
|---|
| PID: | 20.500.12556/RUNG-8171  |
|---|
| COBISS.SI-ID: | 150364419 |
|---|
| DOI: | https://doi.org/10.1103/PhysRevMaterials.7.045604 |
|---|
| NUK URN: | URN:SI:UNG:REP:G8HEHID0 |
|---|
| Publication date in RUNG: | 10.05.2023 |
|---|
| Views: | 456 |
|---|
| Downloads: | 3 |
|---|
| Metadata: |     |
|---|
|
:
|
Copy citation |
|---|
| | | | Average score: | (0 votes) |
|---|
| Your score: | Voting is allowed only for logged in users. |
|---|
| Share: |  |
|---|
Hover the mouse pointer over a document title to show the abstract or click
on the title to get all document metadata. |
