Luigi Giacomazzi (Author), N. S. Shcheblanov (Author), M. E. Povarnitsyn (Author), Yanbo Li (Author), Andraž Mavrič (Author), Barbara Zupančič (Author), Jože Grdadolnik (Author), Alfredo Pasquarello (Author)

Abstract

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.

Keywords

amorphous alumina;infrared spectra;first-principles calculations;

Data

Language: English
Year of publishing:
Typology: 2.20 - Research Data
Organization: UNG - University of Nova Gorica
Publisher: ǂThe ǂMaterials Cloud
UDC: 53
COBISS: 164635907 Link will open in a new window
Views: 55
Downloads: 0
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Other data

Secondary keywords: zbirke podatkov;
Type (COBISS): Not categorized
Pages: 1 spletni vir
DOI: 10.24435/materialscloud:mc-wf
ID: 19933497