Cooling-Rate Effects in Sodium Silicate Glasses: Bridging the Gap between Molecular Dynamics Simulations and Experiments

TL;DR

This study uses molecular dynamics simulations to explore how cooling rates influence sodium silicate glass structure, revealing that medium-range order is affected while short-range order remains stable, and proposes methods to relate simulations to experiments.

Contribution

It bridges the gap between MD simulations and experimental results by analyzing cooling-rate effects on glass structure and providing extrapolation techniques for meaningful comparison.

Findings

Medium-range order varies with cooling rate

Short-range order remains largely unaffected

Proper extrapolation aligns MD results with experiments

Abstract

Although molecular dynamics (MD) simulations are commonly used to predict the structure and properties of glasses, they are intrinsically limited to short time scales, necessitating the use of fast cooling rates. It is therefore challenging to compare results from MD simulations to experimental results for glasses cooled on typical laboratory time scales. Based on MD simulations of a sodium silicate glass with varying cooling rate (from 0.01 to 100 K/ps), here we show that thermal history primarily affects the medium-range order structure, while the short-range order is largely unaffected over the range of cooling rates simulated. This results in a decoupling between the enthalpy and volume relaxation functions, where the enthalpy quickly plateaus as the cooling rate decreases, whereas density exhibits a slower relaxation. Finally, we demonstrate that the outcomes of MD simulations can be meaningfully compared to experimental values if properly extrapolated to slower cooling rates.