Benchmarking boron carbide equation of state using computation and experiment

Area of Science:

• Materials Science and Physics
• Computational Physics
• High-Energy Density Physics

Background:

• Boron carbide (B4C) exhibits complex behavior under compression, with significant industrial and fusion energy applications.
• Accurate equation of state (EOS) data for B4C is crucial for understanding its behavior in extreme environments.
• Previous theoretical models showed discrepancies, particularly in the warm dense matter regime.

Purpose of the Study:

• To perform a comprehensive computational study of the equation of state (EOS) for boron carbide (B4C).
• To investigate B4C in liquid, warm dense matter, and plasma phases across a wide range of temperatures and densities.
• To develop and validate new EOS models for B4C suitable for inertial confinement fusion (ICF) applications.

Main Methods:

• Employed advanced computational techniques including path integral Monte Carlo, activity expansion, and density functional theory-based methods (all-electron Green's function Korringa-Kohn-Rostoker, molecular dynamics).
• Calculated the pressure-internal energy EOS of B4C from ~6x10^3 K to 5x10^8 K and densities from 0.025 to 50 g/cm^3.
• Cross-validated theoretical predictions with Hugoniot measurements up to 61 megabar from National Ignition Facility (NIF) experiments.

Main Results:

• Achieved theoretical prediction discrepancies of less than 5% near the compression maximum (1-2x10^6 K) in the challenging warm-dense state.
• Identified discrepancies of ~18% between first-principles calculations and the Purgatorio model (LEOS 2122) at lower temperatures (6x10^3-2x10^5 K), attributed to ion thermal terms and cold curves.
• Developed three new EOS models consistent with theoretical calculations and experimental data.

Conclusions:

• The developed EOS models provide improved accuracy for B4C under extreme conditions.
• These new models are validated against experimental data and are suitable for use in ICF design studies.
• The study advances the understanding of B4C physics in warm dense matter and plasma regimes.