Characterization of the complex ion dynamics in lithium silicate glasses via computer simulations

TL;DR

This study uses molecular dynamics simulations to analyze lithium ion movement in lithium silicate glasses, revealing detailed dynamics, activation energies, and the separation of vibrational and hopping behaviors across temperature ranges.

Contribution

It provides new insights into lithium ion dynamics in silicate glasses through comprehensive simulation analysis and comparison with experimental data.

Findings

Activation energy matches experimental data

Weak correlation between adjacent ions' dynamics

Identification of localized and long-range dynamic regimes

Abstract

We present results of molecular dynamics simulations on lithium metasilicate over a broad range of temperatures for which the silicate network is frozen in but the lithium ions can still be equilibrated. The lithium dynamics is studied via the analysis of different correlation functions. The activation energy for the lithium mobility agrees very well with experimental data. The correlation of the dynamics of adjacent ions is weak. At low temperatures the dynamics can be separated into local vibrational dynamics and hopping events between adjacent lithium sites. The derivative of the mean square displacement displays several characteristic time regimes. They can be directly mapped onto respective frequency regimes for the conductivity. In particular it is possible to identify time regimes dominated by localized dynamics and long-range dynamics, respectively. The question of time-temperature superposition is discussed for the mean square displacement and the incoherent scattering function.