Investigation of Thermodynamic Perturbation Theory in Fluid Statistical Mechanics

Perturbation theory is a helpful tool in many branches of theoretical physics, and also the statistical mechanics of classical liquids. The perturbation strategy not only plays an important role in bulk fluid thermodynamic properties, but also, in recent year, has become more important in bulk solids, in classical density functional theory and integral equation thermodynamic theory. On the base of thermodynamic perturbation theory, thermodynamic quantities are related to molecular structures via THE radial distribution function and molecular structures are extremely established with hard sphere potential interaction. In the last two decades, there have been advances in all types of theories. All versions of this theory includ 1) Zwanzig approach which expressed so-called high temperature series expansion and formulate the first term of perturbation expansion 2) Barker-Henderson theory for the second order term and higher order terms, and also some modification of Barker-Henderson theory 3) Week-Chandler-Anderson soft-core perturbation theory has been developed by Ben-Amotz and Stell (BAS) via introduction of Boltzmann factor criterion as the effective diameter. In this work, different versions of thermodynamic perturbation theory for the bulk fluids are investigated and Zhou - expansion approach as a new version of thermodynamic perturbation theory will be introduced and compared with the Barker-Henderson macroscopic compressibility approach.