Vibrational dynamics of rutile-type GeO₂ from micro-Raman spectroscopy experiments and first-principles calculations

¹ Department of Physics and Astronomy, University of Padova - Via Marzolo 8, 35131 Padova, Italy
² Groupe Métallogénie Expérimentale, Géosciences Environnement Toulouse GET, University of Toulouse, CNRS - IRD - OMP - Avenue Edouard Belin 14, 31400 Toulouse, France
³ Department of Computer Science, University of Verona - Strada le Grazie 15, 37134 Verona, Italy

Received: 4 December 2014
Accepted: 18 January 2015

Abstract

The vibrational dynamics of germanium dioxide in the rutile structure has been investigated by using polarized micro-Raman scattering spectroscopy coupled with first-principles calculations. Raman spectra were carried out in backscattering geometry at room temperature from micro-crystalline samples either unoriented or oriented by means of a micromanipulator, which enabled successful detection and identification of all the Raman active modes expected on the basis of the group theory. In particular, the E_g mode, incorrectly assigned or not detected in the literature, has been definitively observed by us and unambiguously identified at under excitation by certain laser lines, thus revealing an unusual resonance phenomenon. First-principles calculations within the framework of the density functional theory allow quantifying both wave number and intensity of the Raman vibrational spectra. The excellent agreement between calculated and experimental data corroborates the reliability of our findings.