Stochastic density functional theory combined with Langevin dynamics for warm dense matter

Area of Science:

• Computational Physics
• Quantum Many-Body Theory
• Plasma Physics

Background:

• Warm dense matter (WDM) is a complex state of matter relevant to astrophysics and inertial confinement fusion.
• Accurate theoretical methods are needed to understand WDM properties, but traditional methods face computational challenges.
• Stochastic finite-temperature Kohn-Sham density functional theory (sFT-KSDFT) offers a promising avenue for WDM studies.

Purpose of the Study:

• To extend and apply a recently developed sFT-KSDFT method for WDM simulations.
• To investigate the equation of state, radial distribution, and electronic conductivity of hydrogen under WDM conditions.
• To introduce and validate a linear-scaling stochastic approach for Kubo-Greenwood conductivity calculations.

Main Methods:

• Utilized Langevin dynamics within a stochastic finite-temperature Kohn-Sham density functional theory framework.
• Implemented periodic boundary conditions for simulating bulk matter.
• Developed a linear-scaling stochastic method for calculating Kubo-Greenwood conductivity, ensuring stability for DC conductivity.

Main Results:

• Demonstrated nearly linear scaling of algorithmic complexity with system size and inverse proportionality to temperature.
• Observed a transition from gas-like to liquid-like radial distribution functions for hydrogen at densities above 4 g/cm³ at 30,000 K.
• Identified a notable isosbestic point in electronic conductivity around 7 eV as a function of density, potentially indicating a gas-liquid transition.

Conclusions:

• The extended sFT-KSDFT method provides an efficient and stable computational tool for WDM research.
• The study provides crucial insights into the phase behavior of hydrogen under extreme conditions.
• The observed isosbestic point in conductivity may serve as a new experimental signature for the gas-liquid transition in hydrogen.