LiY(SO$_4$)$_2$: A Superionic Material Synthesized by Superionic State Hidden in no-Superionic Literature

TL;DR

This study identifies LiY(SO$_4$)$_2$ as a superionic material through literature analysis and ab initio calculations, revealing the microscopic mechanisms of cation-anion dynamics that enable superionic behavior.

Contribution

It introduces a novel approach to discovering superionic materials from existing literature and elucidates the microscopic diffusion and reorientation mechanisms involved.

Findings

Li$^+$ diffusion involves changing O neighbor count from 4 to 8

Reorientation of SO$_4^{2-}$ stabilizes superionic state

Micromechanism of cation-anion coupled dynamics explained

Abstract

A potential superionic material LiY(SO$_4$)$_2$ has been excavated from the published literatures because its synthesis method and experiment data implied it exists the superionic state. We use \textit{ab initio} calculation to analyzing the differences between solid state and superionic state. We found the diffusion of Li$^+$ from the lattice site to the interstitial site will change the nearest neighbor numbers of O atom from 4 to 8. In order to reduce energy, the reorientation of SO$_4^{2-}$ must exist accompany with the diffusion of Li$^+$ so the nearest neighbor number of O will keep about 5 in the superionic state. Our work not only presents an example for discovering materials from literatures based on prior knowledge but also reveals the micromechanism of cation-anion coupled dynamics for superionic state.