Enskog and Enskog-Vlasov equations with a modified correlation factor and their H theorem

A modification of the original Enskog equation, which is different from the so-called modified (or revised) Enskog equation, is proposed. The modification changes the correlation factor from a function of density to a functional of density in a simple form without series structure. The present modification is semiphenomenological but is generic to be adapted to a given equation of state for nonideal gases. It is shown that the H theorem can be established for the Enskog and the Enskog-Vlasov equation with the proposed modification.