Statistical Atom Theory and the Equation of State of Solids

Abstract

Recent work indicates that zero-boundary-pressure solutions of the Thomas-Fermi-Dirac (TFD) equation, or of TFD-like equations, probably represent isolated atoms rather than atoms in a crystal of normal density, as is generally tacitly assumed. Partly on this basis, we treat the TFD pressures as only repulsive contributions to the total pressure, and we express the total pressure along the zero-temperature isotherm as the sum of the TFD pressure and an attractive contribution of a type derived from the Morse potential. The experimental isothermal bulk modulus serves to determine the one empirical parameter that appears. Zero-temperature isotherms and shock Hugoniot curves are computed; the latter are in good agreement with experiment.