Extended data set for the equation of state of warm dense hydrogen isotopes

Laser-driven shock wave measurements on hydrogen and deuterium precompressed in diamond anvil cells from 0.16 to 1.6 GPa provide new shock Hugoniot data over a significantly broader range of density-temperature phase space than was previously achievable. Observations of shock velocity and thermal emission provide complete equation of state data (pressure, density, internal energy, and temperature) in the dense fluid regime up to 175 GPa. This data set is used to benchmark recent advanced ab initio calculations and is seen to be in good agreement with a maximum 8% density difference above 100 GPa. Thermodynamic quantities (specific heat and Gruneisen coefficient) are calculated directly from the data and compared to theory. Optical reflectivity data show a continuous transition from an electrically insulating to conducting fluid state and reveal that this transition is increasingly sensitive to temperature with increasing density. Ab initio calculations are observed to underestimate the temperature onset of metallization.