Statistical mechanics of Coulomb gases of arbitrary charge

Publisher Website
Google Scholar
Abstract
The Coulomb-gas activity expansion of Rogers and DeWitt is extended to include more terms. This is an expansion in the activities of electrons and nuclei, and it converges slowly in regions where composite-particles are present. It is shown that by treating certain products of terms as composite-particle activities, the convergence of the expansion is greatly increased. The important element of the present work is the recognition that terms in the original expansion correspond to the Taylor-series expansions of a similar expansion involving an augmented set of activity variables, i.e., the composite particles enter the expansion similar to fundamental particles (electrons and nuclei). This reorganization of the activity expansion makes it possible to calculate the equation of state for electron-nucleus gases of any charge. All stages of ionization and dissociation are treated to the same order of approximation in the new expansion. To illustrate these features some calculations for helium are given. To demonstrate the improved convergence properties, some calculations for hydrogen are compared with those obtained by Rogers and DeWitt.