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

TL;DR

This study uses DFT-based molecular dynamics to analyze how sodium concentration affects the structural properties of sodium thiogermanate glasses, revealing sodium's role in modifying network connectivity and ion organization.

Contribution

It provides detailed insights into the structural evolution of sodium thiogermanate glasses with varying sodium content using first-principles simulations.

Findings

Sodium ions destroy corner-sharing tetrahedral links.

The FSDP disappears and a new pre-peak appears with increasing sodium.

Na-rich zones form at high sodium concentrations.

Abstract

We present a study of the structural 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 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'' FSDP disappears and a new pre-peak appears in the structure factor which can be traced back in the Na-Na partial structure factor. This self organization of the sodium ions is coherent with Na-rich zones that we find at high modifier concentration.