High fidelity equation of state for xenon

Sandia National Laboratories, Albuquerque, New Mexico 87185, USA

^a e-mail: jhcarpe@sandia.gov
^b e-mail: dgflick@sandia.gov
^c e-mail: sroot@sandia.gov
^d e-mail: rjmagya@sandia.gov
^e e-mail: dlhanso@sandia.gov
^f e-mail: trmatts@sandia.gov

Abstract

The noble gas xenon is a particularly interesting element. At standard pressure xenon is an fcc solid which melts at 161 K and then boils at 165 K, thus displaying a rather narrow liquid range on the phase diagram. On the other hand, under pressure the melting point is significantly higher: 3000 K at 30 GPa [1]. Under shock compression, electronic excitations become important at 40 GPa [2]. Finally, xenon forms stable molecules with fluorine (XeF₂) suggesting that the electronic structure is significantly more complex than expected for a noble gas. With these reasons in mind, we studied the xenon Hugoniot using DFT/QMD [3] and validated the simulations with multi-Mbar shock compression experiments. The results show that existing equation of state models lack fidelity and so we developed a wide-range free-energy based equation of state using experimental data and results from first-principles simulations.