Theoretical and experimental investigation of the equation of state of boron plasmas

TL;DR

This paper presents a comprehensive theoretical and experimental study of boron plasmas' equation of state across wide temperature and density ranges, validated by high-pressure shock experiments and advanced first-principles calculations.

Contribution

It provides a validated EOS table for boron using PIMC and DFT-MD methods, combined with high-pressure shock data, advancing understanding of boron under extreme conditions.

Findings

EOS calculations agree within 1.5 Hartree/boron in energy and 5% in pressure

Shock Hugoniot data matches the EOS predictions from first-principles and semi-empirical models

Insights into ionization effects and diffusivity at high pressures and temperatures

Abstract

We report a theoretical equation of state (EOS) table for boron across a wide range of temperatures (5.1$\times$10$^4$-5.2$\times$10$^8$ K) and densities (0.25-49 g/cm$^3$), and experimental shock Hugoniot data at unprecedented high pressures (5608$\pm$118 GPa). The calculations are performed with full, first-principles methods combining path integral Monte Carlo (PIMC) at high temperatures and density functional theory molecular dynamics (DFT-MD) methods at lower temperatures. PIMC and DFT-MD cross-validate each other by providing coherent EOS (difference $<$1.5 Hartree/boron in energy and $<$5% in pressure) at 5.1$\times$10$^5$ K. The Hugoniot measurement is conducted at the National Ignition Facility using a planar shock platform. The pressure-density relation found in our shock experiment is on top of the shock Hugoniot profile predicted with our first-principles EOS and a semi-empirical EOS table (LEOS 50). We investigate the self diffusivity and the effect of thermal and pressure-driven ionization on the EOS and shock compression behavior in high pressure and temperature conditions We study the performance sensitivity of a polar direct-drive exploding pusher platform to pressure variations based on comparison of the first-principles calculations with LEOS 50 via 1D hydrodynamic simulations. The results are valuable for future theoretical and experimental studies and engineering design in high energy density research. (LLNL-JRNL-748227)