Vibrational properties of vitreous GeSe2 with the Becke-Lee-Yang-Parr density functional
The vibrational properties of vitreous GeSe2 are studied within the Becke-Lee-Yang-Parr (BLYP) generalized gradient approximation to density functional theory. For this purpose, we consider two models. The first one is derived from a chemically ordered network, previously generated through classical molecular dynamics. The second one is generated through first-principles molecular dynamics simulations based on the BLYP functional and shows a larger variety of structural motifs. We describe the structural and electronic properties of our models, including bond lengths, first-neighbor coordinations, and the electronic density of states. The vibrational properties are addressed through the vibrational density of states, the infrared spectrum, and the Raman spectrum. For the chemically ordered model, the vibrational properties obtained with the BLYP functional are of comparable quality with respect to previous results obtained with the Perdew-Wang (PW) functional. However, a global consideration of our results indicates that the BLYP functional yields an overall improved description for the vibrational properties of vitreous GeSe2. The BLYP dielectric constants are closer to experimental values. Furthermore, we found that the Raman spectrum of the model generated through first-principles molecular dynamics within the BLYP scheme is largely improved with respect to an analogous model generated within the PW scheme.