Shock compression response of diamond single crystals at multimegabar stresses
J. M. Winey, Marcus D. Knudson, Y. M. Gupta
Abstract
Shock compressed diamond response at multimegabar stresses---of fundamental interest to high pressure science and relevant for high energy density experiments related to inertial confinement fusion---is often assumed to be hydrodynamic. To examine this assumption, plate impact experiments were conducted to measure wave profiles in diamond single crystals shocked to $\ensuremath{\sim}900\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$ elastic impact stress (EIS). For the [110] and [111] orientations, two-wave structures (elastic-inelastic response) were observed to \ensuremath{\sim}900 GPa EIS; in contrast, single (overdriven) waves were observed at 480 GPa EIS and above for the [100] orientation. The elastic wave velocities for the [110] and [111] orientations were significantly larger than those for the [100] orientation. Strong orientation dependence was also observed for the elastic wave amplitudes; for [110] and [111] diamond, the amplitudes increased significantly with increasing elastic impact stress. The observed two-wave structures and the strong orientation dependence (elastic wave speeds and amplitudes) demonstrate unequivocally that the shock response of diamond single crystals is not hydrodynamic at stresses below the melt transition. As such, appropriate elastic-inelastic material descriptions are needed to accurately model the high stress response of diamond and other strong solids.