Perturbation theory and equation of state for dense condensed media

A new variant of thermodynamic perturbation theory in the canonical ensemble with specification of the state of the zeroth approximation is proposed. An equation of state is derived under the assumption that the relative change in the volume is small. This condition holds in a wide range of pressures in dense condensed media far from phase transition points. It is shown that the obtained equation of state can be used in the case of multicomponent systems provided the single-fluid approximation of the mean potential model is valid.