An Equation of State for Condensed Matter behind Intense Shockwaves

Thermodynamic functions that realistically describe characteristics of substances in various parts of the phase diagram are fundamental characteristics of matter. The necessity in such functions has always been urgent and permanently increases. The advanced equations of state constructed to describe the behavior of metals in a broad range of compression parameters contain tens of free parameters and experimentally found constants (see, for instance, [1, 2]). Such constants were found from shock-wave data, from measured unloading isentropes of porous specimens, and from other experimental thermodynamic data. In the present paper, we propose new model equations for thermodynamic functions of crystalline and liquid states based on the dependence of the Gruneisen coefficient Γ(V, T) on volume and temperature. The difference between the elastic (“cold”) components of energy and pressure for a liquid and those for a solid is taken into account. Configurational entropy of a liquid, providing a measure of its disorder and resulting in finite values of the total entropy in the zero-temperature limit, is introduced.