Kinetic energies of liquid and solid phases of $^4$He

TL;DR

This paper uses an advanced Monte Carlo method to accurately compute the kinetic energies of liquid and solid helium-4, comparing different wave functions and aligning well with experimental data.

Contribution

It introduces a multi-weight diffusion Monte Carlo approach combined with the Feynman-Hellmann theorem for precise kinetic energy calculations in helium-4 phases.

Findings

Good agreement with experimental kinetic energies

Symmetry considerations affect solid phase calculations

Method achieves high accuracy in quantum property estimation

Abstract

Kinetic energies of a system of $^4$He are investigated at zero temperature. The multi-weight extension to the diffusion Monte Carlo method is used to implement the Feynman-Hellmann theorem in an effective way. This method allows the quantities of interest to be computed with excellent accuracy. In order to study the importance of symmetry in the kinetic energy calculations, we have considered for the solid phase two guiding wave functions: the Nosanov-Jastrow without boson symmetry and the symmetric Nosanov-Jastrow with boson symmetry. In general very good agreement is found with the experimental data at both the liquid and solid phases.