Microscopic approach to the bcc phase of solid 4He

TL;DR

This study uses path integral Monte Carlo simulations to analyze the microscopic properties and phase transition characteristics between hcp and bcc solid helium-4 at fixed pressure and various temperatures.

Contribution

It provides detailed microscopic energetic and structural data for hcp and bcc phases of solid 4He, highlighting key differences and phase transition indicators.

Findings

Small differences in energetic and structural properties between phases

Significant changes in kinetic energy and Lindemann ratio at phase transition

No off-diagonal long-range order observed in perfect lattices

Abstract

The coexistence between the hcp and bcc phases of solid 4He at fixed pressure, and at three different temperatures, is studied by means of the path integral Monte Carlo method. Microscopic results for the main energetic and structure properties of the two phases are reported. The differences between hcp and bcc 4He are shown to be small with the obvious exception of the static structure factor. When crossing the phase transition line, the most significant changes are observed in the kinetic energy per particle and in the Lindemann ratio, both pointing to a less correlated quantum solid in the bcc side. No off-diagonal long-range order is observed in the the hcp and bcc perfect lattices.