Influence of the cooling-rate on the glass transition temperature and the structural properties of glassy GeS2: an ab initio molecular dynamics study

TL;DR

This study uses ab initio molecular dynamics to explore how different cooling rates affect the glass transition temperature and structural properties of GeS2 glasses, aligning simulation results with experimental data.

Contribution

It provides a detailed analysis of cooling-rate effects on GeS2 glasses using density-functional molecular dynamics, accurately predicting the glass transition temperature and structural features.

Findings

The model accurately predicts the glass transition temperature as a function of cooling rate.

Structural properties from simulations agree well with experimental data across various cooling rates.

Homopolar bonds and charged regions are consistently present in the glassy phase at studied cooling rates.

Abstract

Using density-functional molecular dynamics simulations we analyzed the cooling-rate effects on the physical properties of GeS$_2$ chalcogenide glasses. Liquid samples were cooled linearly in time according to $T(t) = T_0 - \gamma t$ where $\gamma$ is the cooling rate. We found that our model leads to a promising description of the glass transition temperature $T_g$ as a function of $\gamma$ and gives a correct $T_g$ for experimental cooling rates. We also investigated the dependence of the structural properties on the cooling rate. We show that, globally, the properties determined from our simulations are in good agreement with experimental values and this even for the highest cooling rates. In particular, our results confirm that, in the range of cooling rates studied here, homopolar bonds and extended charged regions are always present in the glassy phase. Nevertheless in order to reproduce the experimental intermediate range order of the glass, a maximum cooling rate should not be exceeded in numerical simulations.