New method for determining the Helmholtz energy of a reference system in the WCA method

The method of deriving an expression for calculating the entropy of a liquid with a known pair correlation function proposed earlier by us is applied to a reference system in the Anderson-Weeks-Chandler (WCA) method. As a result, an expression is obtained for the Helmholtz energy that was earlier derived in the WCA method by group expansion with respect to a system of hard spheres. Formulas are presented for the calculation of the entropy and internal energy of the system that significantly simplify the calculation procedure.