We investigate the dissociation and ionization equilibria of deuterium fluid over a wide range of temperatures and densities. The partition functions for molecular and atomic species are evaluated, in a statistical-mechanically consistent way, implementing recent developments in the literature and taking high-density effects into account. A new chemical model (free energy function) is introduced in which the fluid is considered as a mixture of diatomic molecules, atoms, ions and free electrons. Intensive short range hard core repulsion is taken into account together with partial degeneracy of free electrons and Coulomb interactions among charged particles. Samples of computational results are presented as a set of isotherms for the degree of ionization, dissociated fraction of molecules, pressure, and specific internal energy for a wide range of densities and temperatures. Predictions from the present model calculations show an improved and sensible physical behavior compared to other results in the literature.
I -INTRODUCTIONThe equation-of-state of deuterium, over a wide range of densities and temperatures, is of central importance to many fundamental and applied topics and has been under intensive investigation over the past four decades . Accurate prediction of the equation-of-state and thermodynamic properties of deuterium at ultrahigh pressures and a wide range of temperatures is of great interest to ICF research and astrophysical applications. Since the compressibility of a material is determined by its equation-of-state, the accurate estimation of the EOS of the deuterium or deuterium-tritium fusion fuel is critical for designing ICF ignition targets and for predicting the performance of the target during ICF implosions. Besides, both of the planets Jupiter and Saturn contain large amount of very dense hydrogen and information about deuterium EOS is, therefore, essential in the study of these planets.