Pressure and electrical resistivity measurements on hot expanded nickel: comparisons with quantum molecular dynamics simulations and average atom approaches.

We present experimental results on pressure and resistivity on expanded nickel at a density of 0.1 g/cm3 and temperature of a few eV. These data, corresponding to the warm dense matter regime, are used to benchmark different theoretical approaches. A comparison is presented between fully three-dimensional quantum molecular dynamics (QMD) methods, based on density functional theory, with average atom methods, that are essentially one dimensional. In this regime the evaluation of the thermodynamic properties as well as electrical properties is difficult due to the concurrence of density and thermal effects which directly drive the metal-nonmetal transition. Experimental pressures and resistivities are given in a tabular form with temperatures deduced from QMD simulations.