Structural properties of various sodium thiogermanate glasses through DFT-based molecular dynamics simulations

Abstract

We present a study of the structural properties of $(x){\mathrm{Na}}_{2}\mathrm{S}\text{\ensuremath{-}}(1\ensuremath{-}x){\mathrm{GeS}}_{2}$ glasses through density-functional-theory-based molecular dynamics simulations, at different sodium concentrations $(0<x<0.5)$. We computed the radial pair correlation functions as well as the total and partial structure factors. We also analyzed the evolution of the corner- and edge-sharing intertetrahedral links with the sodium concentration and show that the sodium ions exclusively destroy the former. With the increase of the sodium concentration the ``standard'' first sharp diffraction peak disappears and a new prepeak appears in the structure factor which can be traced back in the $\mathrm{Na}\text{\ensuremath{-}}\mathrm{Na}$ partial structure factor. This self-organization of the sodium ions is coherent with Na-rich zones that we find at high modifier concentration.