Dynamical properties of hydrogen fluid at high pressures

Area of Science:

• Physics
• Materials Science
• Computational Chemistry

Background:

• The behavior of hydrogen fluid at high pressures is a key area of scientific interest.
• Experimentally determining dynamical properties of dense hydrogen is challenging.
• Previous studies indicated anomalous diffusion growth in warm dense hydrogen, but the underlying mechanisms remained unclear.

Purpose of the Study:

• To investigate the reasons behind the anomalous diffusion growth in hydrogen fluid at high pressures.
• To reveal the plasma-like behavior contributing to diffusion enhancement.
• To predict diffusion and shear viscosity coefficients using advanced computational methods.

Main Methods:

• Classical molecular dynamics simulations were employed.
• A machine learning potential, developed from ab initio modeling, was utilized.
• Dependencies of vibrational spectrum, molecule lifetime, diffusion, and shear viscosity on density were analyzed across isotherms (600-1100 K).

Main Results:

• The study reveals plasma-like behavior driving the anomalous increase in diffusion coefficients.
• Machine learning potentials enabled precise prediction of diffusion and shear viscosity.
• Dependencies on density and temperature were systematically explored, providing insights into hydrogen's fluid dynamics.

Conclusions:

• The anomalous diffusion in warm dense hydrogen is attributed to plasma-like characteristics.
• Molecular dynamics with machine learning potentials is a powerful tool for studying hydrogen properties.
• This research provides a deeper understanding of hydrogen's behavior under extreme conditions.