Ab initio calculation of elastic properties of solid He under pressure

The high-pressure equation of state and elastic properties of solid He (⁴He) have been calculated using density functional theory formulated in the framework of the exact muffin-tin orbitals method. The theoretical results, obtained within the generalized gradient approximation for the exchange-correlation functional, are in good agreement with the experimental data available for pressures between 13 GPa and 32 GPa. We predict that at 0 K the hexagonal phase of He remains mechanically and thermodynamically stable up to the highest pressure considered in the present study (∼150 GPa). The calculated anisotropy ratios of He are similar to those observed in the case of hexagonal metals with c∕a∼1.63. On the other hand, we find that hydrostatic pressure has negligible effect on the anisotropy of He. This indicates that He can be used as a quasihydrostatic medium in high-pressure experiments up to at least 150 GPa.