Thermodynamic inconsistency of the modified Saha equation at high pressures

Abstract

This paper discusses the thermodynamic inconsistency inherent in the usual approach of using a Saha equation that has been 'corrected' for pressure ionization without making corresponding changes in the expressions for entropy and pressure. It is demonstrated that both the Rouse (1964) and the Stewart-Pyatt (1966) models suffer from this limitation. Negative values of the adiabatic gradient obtained in the degenerate-dwarf models of Boehm (1970, 1972) and Straka (1971) are shown to be prima facie evidence of physical error.