Calculated vibrational and electronic properties of various sodium thiogermanate glasses

TL;DR

This study uses DFT-based molecular dynamics to analyze how sodium concentration affects the vibrational and electronic properties of sodium thiogermanate glasses, revealing mode localization and electronic structure changes.

Contribution

It provides detailed computational insights into vibrational modes, localization, and electronic density of states across varying sodium concentrations in these glasses.

Findings

Na$^+$ ions contribute to the vibrational density of states.

Mode localization varies with sodium content, especially near the Boson peak.

Sodium modifiers significantly alter the electronic density of states.

Abstract

We study the vibrational and electronic properties of (x)Na$_2$S-(1-x)GeS$_2$ glasses through DFT-based molecular dynamics simulations, at different sodium concentrations ($0<x<0.5$). We compute the vibrational density of states for the different samples in order to determine the contribution of the Na$^+$ ions in the VDOS. With an in-depth analysis of the eigenvectors we determine the spatial and atomic localization of the different modes, and in particular in the zone corresponding to the Boson peak. We also calculate the electronic density of states as well as the partial EDOS in order to determine the impact of the introduction of the sodium modifiers on the electronic properties of the GeS$_2$ matrix.