Generalized cluster expansion for real fluids

The equation of state and the pair correlation function of a real fluid is expressed in terms of the equation of state and distribution functions of a reference system. The derived general expression makes it possible to obtain power series for the equation of state, both in powers of a “softness” parameter ξ measuring the “amplitude” of the Boltzmann-factor difference and in powers of a formal parameter λ measuring the “amplitude” of the potential difference (high temperature expansion).