Outside and inside the critical region of the Lennard-Jones fluid

Abstract

The Lennard-Jones (LJ) fluid is studied for states both inside and outside the critical region. Outside the critical region, the mean spherical approximation (MSA) theory is found best for calculating the phase diagram. Inside the critical region, the MSA yields the classical exponents as anticipated. The failure of the MSA and other mean field theories is resolved by a new renormalization group (RG) theory. The new theory is based on a combination of White’s RG transformation, the density functional theory, and the superposition approximation. The new RG theory reduces to White’s RG theory for the van der Waals equation of state and is applicable for other integral equation theories as well as the MSA. An implementation of the MSA+RG transformation for the LJ fluid indicates that nonclassic behavior can be described satisfactorily. An accurate global theory is achieved in this work for the Lennard-Jones fluid.