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Development of a Multiphase Beryllium Equation of State and Physics-based Variations
Christine J Wu1, Philip C Myint1, John E Pask1
1Lawrence Livermore National Laboratory, Livermore, California 94588, United States.
The Journal of Physical Chemistry. A
|February 15, 2021
Summary
We developed new beryllium (Be) equation of state (EOS) models, incorporating DFT calculations for unexplored phases. These models improve understanding of Be behavior under extreme conditions, crucial for fusion energy applications.
Area of Science:
- Materials Science
- Computational Physics
- High-Energy-Density Physics
Background:
- Accurate equation of state (EOS) models for beryllium (Be) are critical for inertial confinement fusion (ICF) research.
- Existing Be EOS models have limitations due to lack of experimental data in high-pressure and high-temperature regimes.
Purpose of the Study:
- To construct a robust family of multiphase beryllium (Be) equation of state (EOS) models.
- To incorporate physics-based uncertainties and validate models with new *ab initio* calculations.
Main Methods:
- Developed a baseline Be EOS model consistent with known phase boundaries, Hugoniot, isobars, and isotherms.
- Employed *ab initio* density functional theory (DFT) and quantum molecular dynamics (QMD) for high-pressure/high-temperature liquid and bcc phases.
- Performed DFT simulations with various exchange-correlation functionals to determine the hcp-bcc transition pressure.
Main Results:
- The baseline EOS predicts a 4.4-fold compression density maximum along the Hugoniot.
- The hcp-bcc-liquid triple-point pressure is predicted at 2.25 Mbar.
- The hcp-bcc transition pressure is bounded to 4 ± 0.5 Mbar, with DFT informing compressibility of the bcc phase.
Conclusions:
- The constructed Be EOS models, including variations for uncertainties, offer a reliable representation for ICF capsule design.
- New DFT data significantly enhances understanding of Be behavior in unexplored phase space.
- The models provide a framework for assessing Be EOS sensitivity in fusion applications.
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