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An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids

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Published on: December 4, 2017

Non-hard sphere thermodynamic perturbation theory.

¹School of Physics Science and Technology, Central South University, Changsha, Hunan 410083, China. chixiayzsq@yahoo.com

The Journal of Chemical Physics

|August 25, 2011

Summary

A new non-hard sphere (HS) perturbation scheme improves thermodynamic perturbation theory (TPT) calculations for various fluids. This advanced method, using coupling parameter expansion (CPE), shows superior accuracy compared to traditional theories.

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Area of Science:

Thermodynamics
Statistical Mechanics
Computational Chemistry

Background:

Traditional thermodynamic perturbation theories often rely on hard sphere (HS) reference potentials.
Developing accurate theoretical models for fluid thermodynamics is crucial for understanding material properties.

Purpose of the Study:

To elaborate on a novel non-hard sphere (HS) perturbation scheme within a coupling parameter expansion (CPE) thermodynamic perturbation framework.
To implement and test the non-HS CPE 3rd-order thermodynamic perturbation theory (TPT) using simulation data.

Main Methods:

NVT-Monte Carlo simulations were performed for a generalized Lennard-Jones (LJ) 2n-n potential.
Thermodynamic quantities were calculated, including excess internal energy, pressure, and free energy.
The non-HS CPE 3rd-order TPT was tested against simulation data and existing literature for hard core attractive Yukawa and Sutherland fluids.

Main Results:

The non-HS CPE 3rd-order TPT demonstrated superior performance compared to traditional theories like van der Waals/HS (vdW/HS) and perturbation theory 2 (PT2)/HS.
Its accuracy was found to be comparable to advanced Ornstein-Zernike integral equation theories.
Key technical aspects influencing the theory's quality include bridge function approximation, reference potential selection, and thermodynamic route choice.

Conclusions:

The non-HS perturbation scheme, when implemented in the CPE framework, offers a promising approach for high-order thermodynamic perturbation theory.
Future advancements in bridge function approximations and reference potential selection will further enhance the accuracy and applicability of this method for diverse model fluids.