Mean spherical approximation for the Lennard-Jones-like two Yukawa model: Comparison against Monte Carlo data

TL;DR

This study compares Monte Carlo simulation results with the mean spherical approximation for a Lennard-Jones-like two Yukawa fluid, examining how the placement of a hard core affects thermodynamic properties across different temperatures.

Contribution

The paper evaluates the accuracy of MSA for LJ2Y fluids with varying hard core positions, providing insights into its applicability under different thermodynamic conditions.

Findings

MSA accurately predicts properties near the critical temperature.

Hard core placement at negative potential energy distances is justified at certain temperatures.

Extreme high-temperature conditions require caution due to property changes.

Abstract

Monte Carlo simulation studies are performed for the Lennard-Jones like two Yukawa (LJ2Y) potential to show how properties of this model fluid depend on the replacement of the soft repulsion by the hard-core repulsion. Different distances for the positioning of hard core have been explored. We have found, that for temperatures that are slightly lower and slightly higher of the critical point temperature for the Lennard-Jones fluid, placing the hard core at distances that are shorter than zero-potential energy is well justified by thermodynamic properties that are practically the same as in original LJ2Y model without hard core. However, going to extreme conditions with the high temperature one should be careful since presence of the hard core provokes changes in the properties of the system. The later is extremely important when the mean spherical approximation (MSA) theory is applied to treat the Lennard-Jones-like fluid.