The not so standard "gold" pressure standard*

A multiphase gold equation of state (EOS) currently under development at Los Alamos is aimed at redefining the commonly used pressure standard through statistical optimization techniques. The pressure standards (Au, Cu, Mo, …) are used as reference materials to establish the relative pressure of other unknown materials. Therefore, any uncertainties in these standards propagate into the evaluation of the unknown material. To reduce the uncertainties in an EOS, we leverage both theoretical calculations and experimental measurements with Markov chain Monte Carlo and Particle Swarm optimization techniques. This optimization provides a means to analyze potential systematic differences in the sampled data (theoretical and experimental) versus modeling choices. As the experimental capabilities continue to push into extreme pressures regions, establishing higher quality pressure standards is necessary. The simple empirical model approximations of the past are not adequate at these new pressure extremes. We will present an overview of the new multiphase EOS and most recent SNL Z Hugoniot data.