Freezing of He-4 and its liquid-solid interface from Density Functional Theory

TL;DR

This paper extends density functional theory to accurately model the solid phase and freezing transition of liquid helium-4 at zero temperature, including interface properties, aligning well with experimental data.

Contribution

The authors develop an extended density functional approach capable of describing solid helium-4 and its interfaces, enabling studies of non-homogeneous systems and nucleation processes.

Findings

Density profiles of liquid-solid interfaces match experimental and microscopic results.

Surface energy and interfacial tension are in semiquantitative agreement with experiments.

The method allows for unbiased studies of helium-4 in complex environments.

Abstract

We show that, at high densities, fully variational solutions of solid-like type can be obtained from a density functional formalism originally designed for liquid 4He. Motivated by this finding, we propose an extension of the method that accurately describes the solid phase and the freezing transition of liquid 4He at zero temperature. The density profile of the interface between liquid and the (0001) surface of the 4He crystal is also investigated, and its surface energy evaluated. The interfacial tension is found to be in semiquantitative agreement with experiments and with other microscopic calculations. This opens the possibility to use unbiased DF methods to study highly non-homogeneous systems, like 4He interacting with strongly attractive impurities/substrates, or the nucleation of the solid phase in the metastable liquid.