Accuracy of Quantum Monte Carlo Methods for Point Defects in Solids

TL;DR

This paper reviews the use of diffusion Monte Carlo methods for calculating point defect energies in solids, discusses the impact of approximations, and provides new estimates for silicon defect formation energies.

Contribution

It offers a comprehensive review of DMC approximations for solids and presents new DMC estimates for silicon point defect formation energies.

Findings

DMC provides highly accurate defect energy calculations.

Approximations significantly influence the accuracy of DMC results.

Predicted formation energies for silicon interstitials are provided.

Abstract

Quantum Monte Carlo approaches such as the diffusion Monte Carlo (DMC) method are among the most accurate many-body methods for extended systems. Their scaling makes them well suited for defect calculations in solids. We review the various approximations needed for DMC calculations of solids and the results of previous DMC calculations for point defects in solids. Finally, we present estimates of how approximations affect the accuracy of calculations for self-interstitial formation energies in silicon and predict DMC values of 4.4(1), 5.1(1) and 4.7(1) eV for the X, T and H interstitial defects, respectively, in a 16(+1)-atom supercell.