Mixing Rules in Dense, Plasma Mixtures

The equation of state (EOS) relates key thermodynamic state variables, such as pressure, volume, and temperature. Mixing rules offer a computationally tractable approach for approximating a multi-component EOS using a combination of results from single-component EOS values. In this work, we construct an EOS model using hypernetted-chain theory (HNC) to not only assess the accuracy of well-known mixing rules, including the Laws of Dalton, Amagat, and Woolley, but also to propose an improved rule. Using the Yukawa (screened Coulomb) interaction, this model computes EOS quantities in terms of the dimensionless Coulomb coupling and screening parameters. The EOS quantities obtained from the HNC calculations are then used to test the given mixing rules. By determining the regimes of validity in the parameter space and quantifying deviations, this study provides a quantitative assessment of the applicability of each mixing rule to non-ideal plasma mixtures.