A new equation of state for dense hydrogen-helium mixtures
Chabrier, G; Mazevet, S; Soubiran, F
Date: 8 January 2019
Journal
Astrophysical Journal
Publisher
American Astronomical Society / IOP Publishing
Publisher DOI
Abstract
We present a new equation of state (EOS) for dense hydrogen/helium mixtures that covers a range of densities
from 10−8 to 106 g cm-3, pressures from 10−9 to 1013 GPa, and temperatures from 102 to 108 K. The calculations
combine the EOS of Saumon, Chabrier & van Horn in the low-density, low-temperature molecular/atomic domain,
the ...
We present a new equation of state (EOS) for dense hydrogen/helium mixtures that covers a range of densities
from 10−8 to 106 g cm-3, pressures from 10−9 to 1013 GPa, and temperatures from 102 to 108 K. The calculations
combine the EOS of Saumon, Chabrier & van Horn in the low-density, low-temperature molecular/atomic domain,
the EOS of Chabrier & Potekhin in the high-density, high-temperature fully ionized domain, the limits of which
differ for H and He, and ab initio quantum molecular dynamics calculations in the regime of intermediate density
and temperature, characteristic of pressure dissociation and ionization. The EOS for the H/He mixture is based on
the so-called additive volume law and thus does not take into account the interactions between the two species. A
major improvement of the present calculations over existing ones is that we calculate the entropy over the entire
density–temperature domain, a necessary quantity for calculations of stellar or planetary evolution. The EOS
results are compared with existing experimental data, namely Hugoniot shock experiments for pure H and He, and
with first-principles numerical simulations for both the single elements and the mixture. This new EOS covers a
wide range of physical and astrophysical conditions, from Jovian planets to solar-type stars, and recovers the
existing relativistic EOS at very high densities, in the domains of white dwarfs and neutron stars. All the tables are
made publicly available.
Physics and Astronomy
Faculty of Environment, Science and Economy
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