EOS author:  Burkhard Militzer  Email: militzer at berkeley dot edu 
In close collaboration with  William B. Hubbard  

Giant planet massradius relation in Jupiter units (figure 12 in Ref. [1])
 Using density
functional molecular dynamics simulations, we determine the equation of
state (EOS) for hydrogenhelium mixtures spanning
densitytemperature conditions typical of giant planet interiors. In
our manuscript [1], a comprehensive equation of state table with 391
densitytemperature points is constructed and the results are presented
in form of twodimensional free energy fit for interpolation. This web
page was setup togive everyone access to our EOS points, the coefficients of the free energy fit, and our free energy interpolation code, which is currently written in Fortran 77. A C++ version could be constructed if there is sufficient demand. We found that our DFTMD simulations led to significant EOS corrections (for details see [1]) to the wellknown, semianalytical SaumonChabriervan Horn EOS, which gave rise to a recalibration of massradius relationship (left figure) in solar and extrasolar giant planets. 
Temperaturedensity conditions were DFTMD simulations were performed (figure 1 in Ref. [1])
 Comments:
This table contains the pressure, internal energy, entropy, and free
energy from our ab initio simulations a hydrogenhelium mixture of a
solartype composition with 18 helium in 220 hydrogen atoms. The helium mass
fraction is Y=0.245. The density parameter r_{s} is given by 4/3*pi*r_{s}^{3}=V/N_{e} where N_{e} is total number of electrons (bound and free) in volume V. The number density of electrons is n=N_{e} / V. The fit uses atomic units: r_{s} is given Bohr radii = 5.29177208607e–11 m F and E are given in Hartree/electron = 4.35974380267e–18 J S is given in k_{b}/electron where k_{b} is Boltzmann's constant. Here is an example for an energy conversion. The zero of energy was set to state of isolated, neutral atoms at rest, which is constistent with the convention in the VASP simulation code. The groundstate energy is the isolate hydrogen molecule using PBE including zeropoint energy then becomes 0.2386100 Hartree per molecule. Limitations: In density, the fit ranges from r_{s}=3.581 to 0.526 [density = 0.06696 ... 19.97757 g/cc, log_{10}(density)=–1.1742 ... 1.3005]. So an alternative EOS table is needed to model the outer envelop of a giant planet where the HHe mixture is at a lower density. The temperature range of the fit is 500 ... 120,000 K [log_{10}(T)=2.6990 ... 5.0792] but only 1,000 ... 80,000 K is based on data from DFTMD simulations. Elsewhere we use an extrapolation. 
Date  File description  Download link 
012913  Fortran 77 code that prints a number of EOS points based on the free energy interpolation  eoshhe_012913.f 
012913  Output of EOS code  eos.out 
012913  Very similar Fortran 77 code that prints the adiabats rather than the EOS points  adhhe_012913.f 
012913  Output of adibat code  ad.out 
013113  Machine readable table of the original EOS points derived from DFTMD simulations  EOS.txt 
013113  Machine readable table of the 2D spline coefficients  EOS_fit.txt 