Theoretical approaches to the structural properties of the   square-shoulder fluid
  A comparison of simulation results with the prediction of the structural properties of square-shoulder fluids is carried out to assess the performance of three theories: Tang--Lu's first-order mean spherical approximation, the simplified exponential approximation of the latter and the rational-function approximation. These three theoretical developments share the characteristic of being analytical in Laplace space and of reducing in the proper limit to the Percus--Yevick result for the hard-sphere fluid. Overall, the best agreement with the simulation data is obtained with the simplified exponential approximation. 
M. L\'opez de Haro, S. B. Yuste, and A. Santos
cond-mat.soft cond-mat.stat-mech physics.chem-ph