Dynamic compression experiments and first-principles simulations on liquid deuterium above the melt boundary to investigate the insulator-to-metal transition

Important phenomena at high pressure, for example in planetary science, occur at conditions that cannot be reached in shock impact experiments. Different techniques have therefore been developed at Sandia's Z-machine. One new approach is shock-ramp loading. The accelerator delivers a two-step current pulse that accelerates the electrode, creating a well-defined shock, and subsequently produces ramp compression from the shocked state. The technique makes it possible to achieve cool (1000-2000 K), high pressure (above 300 GPa), high compression states (10-15 fold) in hydrogen, thus allowing experimental access to the region of phase space where hydrogen is predicted to undergo a first-order phase transition from an insulating molecular liquid to a conducting atomic fluid. Knowing the behavior of hydrogen under these conditions is of pivotal importance to understanding the physics of giant planets. We will survey theoretical predictions for the liquid-liquid insulator-to-metal transition in hydrogen and present the results of experiments on Z.