First Principles Calculations of Shock Compressed Fluid Helium

TL;DR

This study uses first-principles simulations to investigate the behavior of hot dense helium under shock compression, revealing increased compressibility due to electronic excitations and providing maximum compression ratios at extreme conditions.

Contribution

It presents novel first-principles calculations of shock compressed helium, highlighting the role of electronic excitations in its compressibility and predicting maximum compression ratios at high pressures and temperatures.

Findings

Helium's compressibility is significantly increased by electronic excitations.

Maximum compression ratio of 5.24 at 360 GPa and 150000 K.

Helium's maximum compression exceeds that of deuterium.

Abstract

The properties of hot dense helium at megabar pressures were studied with two first-principles computer simulation techniques, path integral Monte Carlo and density functional molecular dynamics. The simulations predicted that the compressibility of helium is substantially increased by electronic excitations that are present in the hot fluid at thermodynamic equilibrium. A maximum compression ratio of 5.24(4)-fold the initial density was predicted for 360 GPa and 150000 K. This result distinguishes helium from deuterium, for which simulations predicted a maximum compression ratio of 4.3(1). Hugoniot curves for statically precompressed samples are also discussed.