Equation of state of boron nitride combining computation, modeling, and experiment

Shuai Zhang, Amy Lazicki, Burkhard Militzer, Lin H. Yang, Kyle Caspersen, Jim A. Gaffney, Markus W. Däne, John E. Pask, Walter R. Johnson, Abhiraj Sharma, Phanish Suryanarayana, Duane D. Johnson, Andrey V. Smirnov, Philip A. Sterne, David Erskine, Richard A. London, Federica Coppari, Damian Swift, Joseph Nilsen, Art J. Nelson, and Heather D. Whitley
Phys. Rev. B 99, 165103 – Published 3 April 2019
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Abstract

The equation of state (EOS) of materials at warm dense conditions poses significant challenges to both theory and experiment. We report a combined computational, modeling, and experimental investigation leveraging new theoretical and experimental capabilities to investigate warm-dense boron nitride (BN). The simulation methodologies include path integral Monte Carlo (PIMC), several density functional theory (DFT) molecular dynamics methods [plane-wave pseudopotential, Fermi operator expansion (FOE), and spectral quadrature (SQ)], activity expansion (actex), and all-electron Green's function Korringa-Kohn-Rostoker (mecca), and compute the pressure and internal energy of BN over a broad range of densities and temperatures. Our experiments were conducted at the Omega laser facility and the Hugoniot response of BN to unprecedented pressures (1200–2650 GPa). The EOSs computed using different methods cross validate one another in the warm-dense matter regime, and the experimental Hugoniot data are in good agreement with our theoretical predictions. By comparing the EOS results from different methods, we assess that the largest discrepancies between theoretical predictions are 4% in pressure and 3% in energy and occur at 106K, slightly below the peak compression that corresponds to the K-shell ionization regime. At these conditions, we find remarkable consistency between the EOS from DFT calculations performed on different platforms and using different exchange-correlation functionals and those from PIMC using free-particle nodes. This provides strong evidence for the accuracy of both PIMC and DFT in the high-pressure, high-temperature regime. Moreover, the recently developed SQ and FOE methods produce EOS data that have significantly smaller statistical error bars than PIMC, and so represent significant advances for efficient computation at high temperatures. The shock Hugoniot predicted by PIMC, actex, and mecca shows a maximum compression ratio of 4.55±0.05 for an initial density of 2.26g/cm3, higher than the Thomas-Fermi predictions by about 5%. In addition, we construct tabular EOS models that are consistent with the first-principles simulations and the experimental data. Our findings clarify the ionic and electronic structure of BN over a broad range of temperatures and densities and quantify their roles in the EOS and properties of this material. The tabular models may be utilized for future simulations of laser-driven experiments that include BN as a candidate ablator material.

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  • Received 2 February 2019

DOI:https://doi.org/10.1103/PhysRevB.99.165103

©2019 American Physical Society

Physics Subject Headings (PhySH)

Interdisciplinary PhysicsPlasma PhysicsCondensed Matter, Materials & Applied Physics

Authors & Affiliations

Shuai Zhang1,*, Amy Lazicki1,†, Burkhard Militzer2,3,‡, Lin H. Yang1, Kyle Caspersen1, Jim A. Gaffney1, Markus W. Däne1, John E. Pask1, Walter R. Johnson4, Abhiraj Sharma5, Phanish Suryanarayana5, Duane D. Johnson6,7, Andrey V. Smirnov6, Philip A. Sterne1, David Erskine1, Richard A. London1, Federica Coppari1, Damian Swift1, Joseph Nilsen1, Art J. Nelson1, and Heather D. Whitley1,§

  • 1Lawrence Livermore National Laboratory, Livermore, California 94550, USA
  • 2Department of Earth and Planetary Science, University of California, Berkeley, California 94720, USA
  • 3Department of Astronomy, University of California, Berkeley, California 94720, USA
  • 4Department of Physics, 225 Nieuwland Science Hall, University of Notre Dame, Notre Dame, Indiana 46556, USA
  • 5College of Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
  • 6Division of Materials Science & Engineering, Ames Laboratory, Ames, Iowa 50011, USA
  • 7Department of Materials Science & Engineering, Iowa State University, Ames, Iowa 50011, USA

  • *zhang49@llnl.gov
  • jenei2@llnl.gov
  • militzer@berkeley.edu
  • §whitley3@llnl.gov

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Issue

Vol. 99, Iss. 16 — 15 April 2019

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