The elastic constants of solid 4He under pressure: a diffusion Monte Carlo study

TL;DR

This study uses diffusion Monte Carlo simulations to accurately determine the elastic constants, sound velocities, and thermodynamic properties of solid 4He under pressure, providing a detailed characterization of its mechanical response at zero temperature.

Contribution

First comprehensive diffusion Monte Carlo calculation of elastic constants and related properties of solid 4He under pressure, with accurate parametrization and comparison to experimental data.

Findings

Elastic constants vary linearly with pressure up to 110 bar.

Good agreement between calculations, previous variational results, and experimental measurements.

Provided zero-temperature values for Gruneisen parameters, sound velocities, and Debye temperature.

Abstract

We study the elasticity of perfect 4He at zero-temperature using the diffusion Monte Carlo method and a realistic semi-empirical pairwise potential to describe the He-He interactions. Specifically, we calculate the value of the elastic constants of hcp helium C_{ij} as a function of pressure up to 110 bar. It is found that the pressure dependence of all five non-zero C_{ij} is linear and we provide accurate parametrization of each of them. Our elastic constants results are compared to previous variational calculations and low-temperature measurements and in general notably good agreement is found among them. Furthermore, we report T = 0 results for the Gruneisen parameters, sound velocities and Debye temperature of hcp 4He. This work represents the first of a series of computational studies aimed at thoroughly characterizing the response of solid helium to external stress-strain.