Molecular dynamics simulation of the free-energy expansion of the square-well fluid of short ranges

► We obtained reliable simulation results for the first three terms of the SW free-energy expansion for ranges ≥ 1.025. ► It is shown that the SW high-temperature expansion, to second order, converges for temperatures greater or equal than 0.5. ► Simulation and a short-range theory are found to agree for the three free-energy terms at the shortest ranges. ► Critical temperatures obtained from the short-range theory have qualitatively sound behavior when the range tends to 1.