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Title:Infrared spectra in amorphous alumina
Authors:ID Giacomazzi, Luigi, Institute of Materials (IOM), National Research Council of Italy (CNR), c/o SISSA Via Bonomea 265, IT-34136 Trieste, Italy (Author)
ID Shcheblanov, Nikita S, Navier, UMR 8205, Ecole des Ponts ParisTech, Univ. Gustave Eiffel, CNRS, 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)
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Typology:2.20 - Complete scientific database of research data
Organization:UNG - University of Nova Gorica
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
PID:20.500.12556/RUNG-8413 New window
COBISS.SI-ID:164635907 New window
DOI:10.24435/materialscloud:mc-wf New window
Publication date in RUNG:15.09.2023
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