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

作者：Hu S X; Militzer B; Collins L A; Driver K P; Kress J D

来源：Physical Review B, 2016, 94(9): 094109.

DOI：10.1103/PhysRevB.94.094109

Shock 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 integralMonte 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 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 shock Hugoniot curve of silicon for pressures varying from similar to 1 Mbar to above similar to 10 Gbar was derived. We find that silicon is similar to 20%, or more, softer than what was predicted by widely used EOS models. Existing high-pressure experimental data (P approximate to 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.

• 出版日期2016-9-15
• 单位Los Alamos