High-pressure properties of diamond (carbon) from shock-wave experiments to 10 Mbar.

The physical behavior of carbon at high pressure, particularly in the diamond phase, is important in planetary settings including terrestrial impact events and the deep interiors of carbon-rich giant planets such as Neptune, and in the laboratory where diamond-anvil cells are used to study the high-pressure behavior of materials. Here, we report recent data on the high-pressure and high-temperature properties of carbon obtained using shock-wave compression experiments on single-crystal diamond. Specifically, we have studied the intrinsic two-shock structure in diamond for shock compression in the 100, 110 and 111 crystallographic orientations. We have examined the limit of the purely-elastic response of diamond, experimentally determining its yield strength. We have measured the equation-of-state and shock Hugoniot of diamond, finding significant deviation from the previously reported shock measurements of Pavlovskii (1971). We have directly observed the melting temperature of diamond at high pressure, and have studied the optical properties of diamond as it transitions from a transparent solid at ambient conditions to a metallic liquid at high pressure and temperature.