Mechanical, elastic and thermodynamic properties of crystalline lithium silicides

TL;DR

This study uses DFT and MEAM-based molecular dynamics to analyze the mechanical and thermodynamic properties of crystalline lithium silicides, providing a fast framework for large unit cell calculations and comparing results with experimental data.

Contribution

It introduces a rapid, accurate computational framework combining DFT and MEAM MD for thermodynamic analysis of complex lithium silicide structures.

Findings

Mechanical properties like bulk modulus are evaluated.

Thermodynamic properties including phonon density of states are calculated.

Temperature effects on heat capacity are studied for Li13Si4.

Abstract

We investigate crystalline thermodynamic stable lithium silicides phases (LixSiy) with density functional theory (DFT) and a force-field method based on modified embedded atoms (MEAM) and compare our results with experimental data. This work presents a fast and accurate framework to calculate thermodynamic properties of crystal structures with large unit cells with MEAM based on molecular dynamics (MD). Mechanical properties like the bulk modulus and the elastic constants are evaluated in addition to thermodynamic properties including the phonon density of states, the vibrational free energy and the isochoric/isobaric specific heat capacity for Li, Li12Si7, Li7Si3, Li13Si4, Li15Si4, Li21Si5, Li17Si4, Li22Si5 and Si. For a selected phase (Li13Si4) we study the effect of a temperature dependent phonon density of states and its effect on the isobaric heat capacity.