Energetics of hydrogen/lithium complexes in silicon analyzed using the Maxwell construction

TL;DR

This paper introduces a graphical method based on the Maxwell construction to analyze the stability of hydrogen and lithium complexes in silicon, relevant for lithium-ion battery anodes, revealing stable complex formations involving hydrogen and lithium.

Contribution

A novel visualization approach using convex hull diagrams and Maxwell construction to assess defect stability in silicon with hydrogen and lithium impurities.

Findings

Hydrogen binds to lithium clusters forming stable complexes.

The {H,3Li} and {2H,3Li} complexes are stable in silicon.

The {H,2Li} complex is nearly stable.

Abstract

We have studied hydrogen/lithium complexes in crystalline silicon using density-functional-theory methods and the ab initio random structure searching (AIRSS) method for predicting structures. A method based on the Maxwell construction and convex hull diagrams is introduced which gives a graphical representation of the relative stabilities of point defects in a crystal and enables visualization of the changes in stability when the chemical potentials are altered. We have used this approach to study lithium and hydrogen impurities in silicon, which models aspects of the anode material in the recently-suggested lithium-ion batteries. We show that hydrogen may play a role in these anodes, finding that hydrogen atoms bind to three-atom lithium clusters in silicon, forming stable {H,3Li} and {2H,3Li} complexes, while the {H,2Li} complex is almost stable.