The Equations of State of Hydrogen and Argon: Applications to the Jovian Interior

Citation

Lagus, Peter Leonard (1974) The Equations of State of Hydrogen and Argon: Applications to the Jovian Interior. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/zzpq-2876. https://resolver.caltech.edu/CaltechTHESIS:12072020-234014838

Abstract

Hugoniot data for solid argon (initially at 77°K and l bar) and solid hydrogen (initially at 5°K and 1 bar) have been obtained to 143 kbar and 6.4 kbar respectively utilizing a propellant gun. The argon data (at volumes of 15.28, 14.84 and 14.64 cc/mole) are in fair agreement with previous shock data, and in excellent agreement with recent theoretically predicted Hugoniots. The hydrogen data (at volumes of 17.10, 15.32, 15.27, 15.11 cc/mole) are compared with Hugoniots calculated from published isothermal compression data. For both argon and hydrogen, the present data are consistent with the assumption that γ/V is constant. Furthermore, to compressions of V/V₀ ≃ 0.65, no gross inconsistencies exist between shock-wave and isothermal compression measurements in solid hydrogen.

A simple equation of state (E0S) for molecular hydrogen based on a spherically averaged De Boer-type repulsion potential which explicitly includes the zero point energy reproduces experimental pressure-volume data between 5 kbar and 370 kbar. This molecular equa­tion of state when combined with recent metallic equations of state implies a molecular to metallic phase transition pressure of 1.9 ± 0.4 Mbar at 0°K.

A thermally expanded model of Jupiter which incorporates this molecular equation of state, recent metallic hydrogen and helium equa­tions of state, and a van der Waals-type atmosphere yields a model with a hydrogen abundance of x = 0.57. However, the interior temperatures are everywhere above the melting temperature of metallic hydrogen.

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