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This content will become publicly available on September 15, 2017

Title: First-principles prediction of the softening of the silicon shock Hugoniot curve

Here, whock compression of silicon (Si) under extremely high pressures (>100 Mbar) was investigated by using two first-principles methods of orbital-free molecular dynamics (OFMD) and path integral Monte Carlo (PIMC). While pressures from the two methods agree very well, PIMC predicts a second compression maximum because of 1s electron ionization that is absent in OFMD calculations since Thomas–Fermi-based theories lack inner shell structure. The Kohn–Sham density functional theory is used to calculate the equation of state (EOS) of warm dense silicon for low-pressure loadings (P < 100 Mbar). Combining these first-principles EOS results, the principal Hugoniot curve of silicon for pressures varying from 0.80 Mbar to above ~10 Gbar was derived. We find that silicon is ~20% or more softer than what was predicted by EOS models based on the chemical picture of matter. Existing experimental data (P ≈ 1–2 Mbar) seem to indicate this softening behavior of Si, which calls for future strong-shock experiments (P > 10 Mbar) to benchmark our results.
 [1] ;  [2] ;  [3] ;  [2] ;  [3]
  1. Univ. of Rochester, Rochester, NY (United States)
  2. Univ. of California, Berkeley, CA (United States)
  3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
OSTI Identifier:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 94; Journal Issue: 9; Journal ID: ISSN 2469-9950
American Physical Society (APS)
Research Org:
Univ. of Rochester, Rochester, NY (United States). Lab. for Laser Energetics
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States