Statistical mechanics of light elements at high pressure. VII  A perturbative free energy for arbitrary mixtures of H and He
Abstract
A model free energy is presented which accurately represents results from 45 highprecision Monte Carlo calculations of the thermodynamics of hydrogenhelium mixtures at pressures of astrophysical and planetophysical interest. The free energy is calculated using freeelectron perturbation theory (dielectric function theory), and is an extension of the expression given in an earlier paper in this series. However, it fits the Monte Carlo results more accurately, and is valid for the full range of compositions from pure hydrogen to pure helium. Using the new free energy, the phase diagram of mixtures of liquid metallic hydrogen and helium is calculated and compared with earlier results. Sample results for mixing volumes are also presented, and the new free energy expression is used to compute a theoretical Jovian adiabat and compare the adiabat with results from threedimensional ThomasFermiDirac theory. The present theory gives slightly higher densities at pressures of about 10 megabars.
 Publication:

The Astrophysical Journal
 Pub Date:
 March 1985
 DOI:
 10.1086/162996
 Bibcode:
 1985ApJ...290..388H
 Keywords:

 Computational Astrophysics;
 Light Elements;
 Statistical Mechanics;
 Coulomb Collisions;
 Free Energy;
 Gas Dynamics;
 Gas Mixtures;
 Helium;
 High Pressure;
 Hydrogen;
 Jupiter (Planet);
 Monte Carlo Method;
 Perturbation Theory;
 Astrophysics