Soft core thermodynamics from self-consistent hard core fluids

Area of Science:

• Statistical Mechanics
• Liquid State Theory
• Computational Chemistry

Background:

• The self-consistent Ornstein-Zernike approximation (SCOZA) is an accurate liquid state theory.
• SCOZA has been limited to hard core systems.
• Perturbation theory offers a way to extend theories to soft core systems.

Purpose of the Study:

• To generalize SCOZA to arbitrary soft core systems.
• To combine SCOZA with a perturbation theory developed by Ben-Amotz and Stell.
• To assess the accuracy of the combined approach for the Lennard-Jones fluid.

Main Methods:

• Combining SCOZA with a perturbation theory based on an arbitrary hard sphere reference system.
• Reformulating the Weeks-Chandler-Andersen perturbation theory.
• Comparing predictions with simulation data and pure perturbation theory.

Main Results:

• The combined SCOZA and perturbation theory approach shows accuracy for the Lennard-Jones fluid.
• Thermodynamic properties and phase behavior are sensitive to the effective hard core diameter.
• The generalization allows SCOZA to be applied to soft core systems.

Conclusions:

• The combined approach successfully generalizes SCOZA to soft core systems.
• The method provides accurate predictions for thermodynamic properties and phase behavior.
• The choice of reference system diameter is crucial for accurate results.