Self-diffusion coefficient as a function of the thermodynamic factor.

Area of Science:

• Thermodynamics
• Fluid Dynamics
• Statistical Mechanics

Background:

• Existing theories for dense fluids often lack broad applicability across different particle types or concentrations.
• Rosenfeld's theory linked self-diffusion coefficient to excess entropy, but a more general approach is needed.

Purpose of the Study:

• To develop a novel theory for self-diffusion in dense fluids.
• To utilize thermodynamic factors, specifically the excess chemical potential, as a basis for diffusion theory.
• To create a model applicable across various interaction potentials without parameter readjustment.

Main Methods:

• Developed a theoretical model based on the thermodynamic factor and excess chemical potential.
• Validated the model using molecular dynamics simulations for hard spheres.
• Tested the model's transferability using simulations for a Lennard-Jones gas.

Main Results:

• The model was successfully fitted to hard sphere simulation data using two free parameters.
• The same parameters accurately predicted diffusion for the Lennard-Jones gas, demonstrating model transferability.
• The model shows promise for describing experimental data, particularly in high-density regimes.

Conclusions:

• The proposed model offers a more universally applicable approach to dense fluid diffusion.
• Using thermodynamic factors provides a robust framework that transcends specific interaction potentials.
• The model's success with hard spheres and Lennard-Jones systems suggests potential for broader applications, including experimental data analysis like xenon self-diffusion.