Pressure induced Structure Change and Anomalies in Thermodynamic Quantities and Transport Properties in Liquid Lithium Hydride

TL;DR

This study uses first-principles simulations to reveal how liquid lithium hydride undergoes a pressure-induced structural crossover, significantly affecting its thermodynamic and transport properties, and provides a detailed phase diagram.

Contribution

First to predict pressure-induced structural crossover and anomalies in thermodynamic and transport properties of liquid LiH using ab initio molecular dynamics.

Findings

Identified a continuous crossover from duality symmetry to broken symmetry in liquid LiH under pressure.

Observed significant changes in heat capacity and ionic diffusivity with pressure.

Constructed a comprehensive high-pressure phase diagram for LiH.

Abstract

Understand the nature of liquid structure and its evolution under different conditions is a major challenge in condensed physics and materials science. Here, we report a pressure-induced structure change spanning a wide pressure range in liquid-state lithium hydride (LiH) by first-principles molecular dynamic simulations. This behavior can be described as a continuous crossover from low pressure liquid with Li$^+$-H$^-$ duality symmetry to high pressure one with broken of duality symmetry. The thermodynamic quantities such as heat capacity and ionic transport properties such as diffusivity are also saliently impacted. It is important to stress that such behavior is firstly predicted for this category of materials, which is ubiquitous in universe as well as in industry applications. Lastly, a comprehensive high-pressure high-temperature phase diagram of LiH is constructed, which embodies rich physics in this previously-thought-simple ionic compound.