Lithium Diffusion in Li2X(X=O, S and Se): Ab-initio Simulations and Neutron Inelastic Scattering Measurements

TL;DR

This study combines ab-initio simulations and neutron scattering to explore lithium diffusion mechanisms and transition temperatures in Li2X compounds, revealing how chemical pressure influences superionic behavior.

Contribution

It introduces a comprehensive approach integrating simulations and experiments to analyze ionic conduction and transition temperatures in Li2X materials.

Findings

Neutron spectra change significantly at superionic transition.

Diffusion pathways are identified through simulations.

Chemical pressure correlates with transition temperature.

Abstract

We have performed ab-initio lattice dynamics and molecular dynamics studies of Li2X (X=O, S and Se) to understand the ionic conduction in these compounds. The inelastic neutron scattering measurements on Li2O have been performed across its superionic transition temperature of about 1200 K. The experimental spectra show significant changes around the superionic transition temperature, which is attributed to large diffusion of lithium as well as its large vibrational amplitude. We have identified a correlation between the chemical pressure (ionic radius of X atom) and the superionic transition temperature. The simulations are able to provide the ionic diffusion pathways in Li2X.