High-temperature expansion of the mean spherical approximation for hard-core two-Yukawa simple and chain fluids

Analytic compressibility factors and internal energies for hard-core two-Yukawa (HCTY) simple fluids are obtained by using the high-temperature expansion of the mean spherical approximation. The analytical formulae thus derived are in good agreement with the full numerical mean spherical approximation (MSA) calculations and the Monte Carlo simulations recently performed on different combination cases of the two Yukawa potentials outside the hard core. These cases describe various physical interactions such as that between charged colloid particles or the Lennard–Jones LJ(12,6) function. The above thermodynamic quantities are then combined with the statistical associating fluid theory of chain fluids so as to obtain in analytical form the compressibility factor and the internal energy of a fluid composed of m freely jointed tangent monomers which interact through a HCTY potential. The resulting expressions are simple and represent accurately the Monte Carlo simulations recently performed on both dimer and tetramer fluids with a HCTY potential that fits the L(12,6) potential outside the hard core.