Semiempirical Model of Equation of State for Condensed Media

An approximation of equation of state for matter is treated, which involves the consistent use of interpolation approach with respect to both density and temperature in the entire nonrelativistic region. The cold component is defined under normal conditions by four experimentally obtained parameters, namely, specific volume, bond energy, bulk modulus, and parameter $\kappa = -(\partial\ln B_S/\partial\ln V)_S$. The thermal ion component describes the transition from lattice vibrations with free Debye energy as a function of characteristic temperature being introduced, which makes possible the extension of the range of its application from zero temperature to ideal gas. The thermal electron component describes the transition of free electrons from ideal degenerate gas to nondegenerate state. A formula is suggested which enables one to calculate the degree of ionization at arbitrary densities and temperatures. Continuous functions are described which approximate ionization potentials and energies. The phase diagram, shock adiabats for continuous and porous matter, and isentropes are calculated. An analytical approximation of the Debye function is suggested. The results are illustrated by dependences on compression ratio in the range $\rho/\rho_0 = 1$–$10^6$. Comparison is made with experimental data.