First-principles equation of state of gold

Abstract

The equation of state of gold is calculated to combined pressures and temperatures of 200 GPa and 5000 K using the linear muffin-tin orbitals (LMTO) technique with approximate corrections for lattice vibrational and electronic contributions to the pressure. Comparisons with existing static-compression, shock-compression (Hugoniot), and ultrasonic measurements show good agreement with the theoretical results: for example, the theoretically predicted 300-K isotherm agrees to within 2 GPa with the isotherm that has been measured to 70 GPa. Our calculations show that the electronic contribution to the high-temperature equation of state is negligibly small and that gold behaves simply under compression, with virtually no change in electronic structure. This conclusion and the good agreement between theory and experiment support the use of gold as an ultrahigh-pressure–temperature-calibration standard.