Slow Dynamics in Ion-Conducting Sodium Silicate Melts: Simulation and Mode-Coupling Theory

TL;DR

This study combines molecular dynamics simulations and mode-coupling theory to explain the slow ion dynamics in sodium silicate melts, highlighting sodium diffusion channels and their impact on relaxation times.

Contribution

It demonstrates that mode-coupling theory, using static structure factors from simulations, can accurately reproduce sodium-ion dynamics in sodium silicate melts.

Findings

Mode-coupling theory reproduces relaxation time scales.

Identification of sodium diffusion channels via static structure factors.

Explanation of fast sodium-ion dynamics using microscopic theory.

Abstract

A combination of molecular-dynamics (MD) computer simulation and mode-coupling theory (MCT) is used to elucidate the structure-dynamics relation in sodium-silicate melts (NSx) of varying sodium concentration. Using only the partial static structure factors from the MD as an input, MCT reproduces the large separation in relaxation time scales of the sodium and the silicon/oxygen components. This confirms the idea of sodium diffusion channels which are reflected by a prepeak in the static structure factors around 0.95 A^-1, and shows that it is possible to explain the fast sodium-ion dynamics peculiar to these mixtures using a microscopic theory.