Quantum Monte Carlo Compton profiles of solid and liquid lithium

TL;DR

This study uses quantum Monte Carlo methods to accurately compute and compare the Compton profiles of solid and liquid lithium, emphasizing the importance of core-valence orthogonalization and density effects for agreement with experimental data.

Contribution

It presents the first all-electron QMC benchmark for lithium's Compton profile and introduces pseudopotential corrections for liquid and solid states.

Findings

Good agreement with experimental measurements

Importance of core-valence orthogonalization highlighted

First all-electron QMC benchmark for lithium

Abstract

We computed the Compton profile of solid and liquid lithium using quantum Monte Carlo (QMC) and compared with recent experimental measurements obtaining good agreement. Importantly, we find it crucial to account for proper core-valence orthogonalization and to address density differences when comparing with experiment. To account for disorder effects, we sampled finite-temperature configurations using molecular dynamics (MD), then performed diffusion Monte Carlo (DMC) simulations on each configuration. We used Slater-Jastrow wavefunctions and grand-canonical twist-averaged boundary conditions. A QMC pseudopotential correction, derived from an all-electron DMC simulation of the perfect crystal was also used. Our calculations provide the first all-electron QMC benchmark for the Compton profile of lithium crystal and pseudopotential-corrected QMC Compton profiles for both the liquid and solid.