A modified soft-core fluid model for the direct correlation function of the square-shoulder and square-well fluids

► Analytic direct correlation functions for simple fluids are obtained. ► Our approach is based on a rescaling of the hard-core direct correlation function. ► Our findings agree well with the Percus-Yevick approximation and MC simulations. ► The analytic functions reproduce the thermodynamics above the critical temperature. ► Our analytical functions might be easily incorporated as new reference systems.