Vibrational dynamics of anataseTiO2: Polarized Raman spectroscopy andab initiocalculations

Abstract

Vibrational properties of anatase titanium dioxide single crystal are thoroughly investigated by means both of experimental and theoretical approaches. Polarized Raman-scattering experiments were carried out at room temperature in backscattering geometry on a microcrystalline anatase sample under different crystal orientations set by a micromanipulator. All the independent components of the polarizability tensor were separately obtained. In particular, it was possible to evidence, in turn, the different components of the ${\text{A}}_{1g}$ mode, thus unambiguously determining its peak wave number, and then, definitively resolve and identify the ${\text{A}}_{1g}$ and ${\text{B}}_{1g}$ modes of anatase. Moreover, ab initio calculations based on density-functional perturbation theory within the generalized gradient approximation have been performed to evaluate infrared (IR) and Raman modes, dielectric tensors, Born effective charges and TO-LO splitting of the IR modes. The agreement between computational and experimental results is much better than the one achieved in previous computational works.