Compressibility of solid helium

TL;DR

This study uses path-integral Monte Carlo simulations to analyze the compressibility, bulk modulus, isotopic effects, and thermal expansion of solid helium across various phases, temperatures, and pressures, providing detailed insights into its physical properties.

Contribution

It presents the first comprehensive simulation-based analysis of solid helium's compressibility, isotopic effects, and thermal expansion over a wide range of conditions.

Findings

Bulk modulus decreases by about 10% from low temperature to melting point at 4-10 GPa.

Isotopic difference in bulk modulus is approximately 2% at 25 K and 1 GPa.

Thermal expansion coefficients are quantified across different phases and conditions.

Abstract

The compressibility of solid helium (3He and 4He) in the hcp and fcc phases has been studied by path-integral Monte Carlo. Simulations were carried out in both canonical (NVT) and isothermal-isobaric (NPT) ensembles at temperatures between 10 and 300 K, showing consistent results in both ensembles. For pressures between 4 and 10 GPa, the bulk modulus B is found to decrease by about 10 %, when temperature increases from the low-temperature limit to the melting temperature. The isotopic effect on the bulk modulus of helium crystals has been quantified in a wide range of parameters. At 25 K and pressures on the order of 1 GPa, the relative difference between 3He and 4He amounts to about 2 %. The thermal expansion has been also quantified from results obtained in both NPT and NVT simulations.