Shock equation of state of LiH6 to 1.1 TPa

• Published in: Physical review. B 2017-10, Vol.96 (13)
• Main Authors: Lazicki, A, London, R A, Coppari, F, Erskine, D, Whitley, H D, Caspersen, K J, Fratanduono, D E, Morales, M A, Celliers, P M, Eggert, J H, Millot, M, Swift, D C, Collins, G W, Kucheyev, S O, Castor, J I, Nilsen, J
• Format: Article
• Language: English
• Subjects: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Ab initio calculations; Computer simulation; Density; Equations of state; First-principles calculations in plasma physics; Free energy; Gruneisen parameter; High-energy-density plasmas; Hot dense plasma; Hugoniot curves; Ionization; Laser techniques; Molecular dynamics; Optical interferometry; Optical plasma measurements; Plasma physics; Plasma production & heating by laser beams, laser-foil, laser-cluster; Plasma production & heating by shock waves & compression; Pressure effects; Shock waves; Temperature
• ISSN: 2469-9950; 2469-9969

Using laser-generated shock waves, we have measured pressure, density, and temperature of LiH on the principal Hugoniot between 260 and 1100 GPa (2.6–11 Mbar) and on a second-shock Hugoniot up to 1400 GPa to near fivefold compression, extending the maximum pressure reached in non-nuclear experiments by a factor of two. We observe the onset of metal-like reflectivity consistent with temperature-induced ionization of the Li 2s electron, and no sign of additional changes in ionization up to the maximum pressure. Our measurements are in good agreement with gas gun, Z-machine, and underground test data and are accurately described by quantum molecular dynamics simulations. The results confirm the validity of equation of state models built on an average-atom description of the electron-thermal contribution to the free energy and a density-dependent Grüneisen parameter to describe shock response of LiH over this pressure range.