  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.
