Equilibrium Properties of a Multicomponent Ionized Gas

Abstract

A method has been developed for the calculation of the equilibrium properties of an ionized gas consisting of many nuclear and molecular species. An essential feature of the present calculation is that it explicitly considers more than one ionic species per atom and therefore applies to partially ionized atoms and molecules. Free and bound electrons are distinguished by counting as bound electrons all those in the ground state of each ionic species. Molecular species with internal degrees of freedom are also included. The additivity of kinetic and potential energy is assumed, a classical electrostatic potential of interaction is used, and electron degeneracy is included only in the kinetic energy terms. The Helmholtz free energy of the system is minimized with respect to the concentration of each species assumed present, thus determining the equilibrium composition of the system as a function of temperature and volume. The thermodynamic quantities of interest are then calculated for an appropriate temperature‐volume grid. This method thus allows the effect of the variation of composition on the equation of state to be determined, as well as the delineation of regions in PVT space where the electron degeneracy and electrostatic interaction each becomes important. The present model is applied to a system of particles arising from the hydrogen molecule.