Thermodynamically Consistent Equations of State

Abstract

The equation of state for gaseous plasma is well described bу the Saha model. In this work, accounting for the finite ion core volume is included in this model. This improvement allows the expansion of the Saha model to superhigh densities and moderate temperatures, where plasma can be considered as a liquid. In this domain, the thermodynamics of the Saha model is quite close to that of the Thomas–Fermi model with corrections (TFC), which is conventionally used for condensed matter. This improved the agreement of the theory with experimental data. Using a special interpolation, the Saha model and the TFC model are united in a single equation of state, in which the strict thermodynamic consistency of all quantities is provided. The latter is very important for the application of the equation of state in gasdynamic calculations.