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

Abstract

Brillouin scattering spectra of fluid hydrogen were measured at high pressures ͑1 to 13 GPa͒ and temperatures ͑293 to 526 K͒. 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.

The properties of hydrogen and helium under extreme conditions

“…To remedy this Ross et al, 1983 proposed a modified effective potential, the Ross, Ree, and Young (RRY) potential, by softening the SG potential at short range. Further improvements to match experimental data at higher pressures and temperatures in the liquid phase have been proposed by Ross, Ree and Young and by Hemley, and tested in Matsuishi et al, 2003. Unfortunately, the transferability of effective potentials (i.e.…”

Probing dynamic crystal growth of compressed hydrogen using dynamic-DAC, time-resolved spectroscopy and highspeed micro-photography

“…The heat of fusion can be calculated from the Clapeyron equation using the well established melt curve, [20], and theoretically calculated change in volume ΔV = 0.27 cm -1 /mol [21]. The constant pressure heat capacity was taken from [22] to be C p = 14.49 J/mol K extrapolated for the melting temperature at T m = 298 K. The calculated change in temperature was found to be ΔT ≈ 174 K in an adiabatic system. Given that the hydrogen sample is in direct contact with the diamond face, heat release from the sample would be almost instantaneously absorbed by diamond preventing an appreciable heating of the bulk hydrogen sample.…”

Thermodynamics of Formation of the Hydrogenated Permalloy under High Pressure on the Basis of the Approach from the First Principles

“…К сожалению, к настоящему времени теоретические расчёты фазовой диаграммы водорода в широком интервале давлений и температур не обеспечи-вают достаточного согласия с экспериментальными данными (см. обзорную статью [33] и более современные работы [34,35]). В то же время в работе [33] предложено трёхпараметричёское феноменоло-гическое уравнение состояния водорода, полученное интерполяци-ей экспериментальных данных по широкому интервалу давлений на основе уравнения состояния Вине [36], вплоть до рентгеновской дифрактометрии кристаллического водорода в алмазной наковаль-не: , V 0 и  0  0,0435 мольсм 3 есть моляр-ный объем и плотность кристаллического водорода при атмосфер-ном давлении и нулевой температуре, K 0  0,1724 ГПа -модуль всестороннего сжатия,   1,5( 0 K  1), 00 7,194 K dK dP   .…”