Abstract
We use path integral Monte Carlo and density functional molecular dynamics to construct a coherent set of equations of state (EOS) for a series of hydrocarbon materials with various C:H ratios (2:1, 1:1, 2:3, 1:2, and 1:4) over the range of and . The shock Hugoniot curve derived for each material displays a single compression maximum corresponding to -shell ionization. For C:H = 1:1, the compression maximum occurs at 4.7-fold of the initial density and we show radiation effects significantly increase the shock compression ratio above 2 Gbar, surpassing relativistic effects. The single-peaked structure of the Hugoniot curves contrasts with previous work on higher- plasmas, which exhibit a two-peak structure corresponding to both - and -shell ionization. Analysis of the electronic density of states reveals that the change in Hugoniot structure is due to merging of the -shell eigenstates in carbon, while they remain distinct for higher- elements. Finally, we show that the isobaric-isothermal linear mixing rule for carbon and hydrogen EOS is a reasonable approximation with errors better than 1% for stellar-core conditions.
- Received 30 January 2017
DOI:https://doi.org/10.1103/PhysRevE.96.013204
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