Equation of state and intermolecular interactions in fluid hydrogen from Brillouin scattering at high pressures and temperatures

Brillouin scattering spectra of fluid hydrogen were measured at high pressures (1 to 13 GPa) and temperatures (293 to 526 K). From these sound velocity data together with previously reported volume and ultrasonic velocity data at low pressures and temperatures, we determined a Benedict-type P-V-T equation of state valid for fluid hydrogen up to the maximum pressures and temperatures of this study with an average deviation of 1.0% from the new and previously published experimental data. Using the equation of state, the pressure and temperature dependences of thermodynamic properties were calculated. We examined three types of intermolecular potentials for fluid hydrogen, and found that the Hemley-Silvera-Goldman potential gives superior fits to the experimentally derived equation of state over a wide temperature range above 6 GPa. Discrepancies found in the high temperature range at low pressures provide additional constraints on determination of the intermolecular potential. (C) 2003 American Institute of Physics.