An equation of state for more than two phases, with an application to the Earth's mantle

Abstract

A general equation of state for fluids of any number of phases is derived. The equation contains the principal experimental state equations as special cases. The non–additive energies of 3, 4, ... particles must also be considered, plus the additive binary energies. In order to derive the isotherm in the vicinity of a critical point, it is found that the equation of state must contain at least three parameters, including the non–additive three–body potential energy. We show how to obtain the interaction spectra of an equation of state for the earth's mantle.