The high temperature approximation and linearity of the thermodynamic properties on the WCA perturbation parameter

Abstract

Abstract We carried out extensive computer simulations to obtain the radial distribution function, potential energy per particle and pressure for three-dimensional Lennard-Jones fluids. Each thermodynamic state (265 in total) was simulated for five values of the perturbative parameter of the Weeks-Chandler-Andersen theory. The results show that, for the Helmholtz free energy, the high temperature approximation works very well for all the temperatures and densities studied here, for the potential energy it is good at moderate and high densities for all temperatures, whereas for the pressure it is generally not good. In accordance with other works, for the radial distribution function the high temperature approximation can be used at high densities only. The linearity of the thermodynamic properties, with respect to the perturbative parameter of this theory was also analysed. The results show that the Helmholtz free energy, potential energy per particle and pressure are linear in the mentioned parameter for all densities and temperatures.