First principles calculations of shock compressed fluid helium

Area of Science:

• Condensed matter physics
• Computational physics
• High-pressure physics

Background:

• Understanding the behavior of matter under extreme conditions is crucial for astrophysics and materials science.
• Helium, a fundamental element, exhibits unique properties when subjected to high pressures and temperatures.

Purpose of the Study:

• To investigate the properties of hot, dense helium at megabar pressures.
• To determine the effect of electronic excitations on helium's compressibility.
• To compare helium's compression behavior with that of deuterium.

Main Methods:

• Utilizing two first-principles computer simulation techniques: path integral Monte Carlo (PIMC) and density functional molecular dynamics (DFMD).
• Simulating helium at thermodynamic equilibrium under high-pressure conditions.

Main Results:

• Electronic excitations significantly enhance the compressibility of hot, dense helium.
• A maximum compression ratio of 5.24(4) was predicted at 360 GPa and 150,000 K.
• Helium's compression behavior differs from deuterium, which showed a maximum ratio of 4.3(1) under similar simulation conditions.

Conclusions:

• Electronic excitations play a critical role in the compressibility of hot dense helium.
• Helium's response to extreme pressure is distinct from other light elements like deuterium.
• The study provides valuable data for understanding planetary interiors and inertial confinement fusion scenarios.