Mean force kinetic theory applied to self-diffusion in supercritical Lennard-Jones fluids

Area of Science:

• Thermodynamics
• Statistical Mechanics
• Fluid Dynamics

Background:

• Accurate calculation of transport properties is crucial for understanding dense fluid behavior.
• Existing theories like free-volume theory have limitations, especially for systems with long-range interactions.

Purpose of the Study:

• To present a novel kinetic-theory-based calculation for self-diffusion coefficients in dense supercritical Lennard-Jones fluids.
• To validate this new approach against molecular dynamics simulations and compare it with existing theories.

Main Methods:

• Application of the mean force kinetic theory, originally developed for dense plasmas, to neutral fluids.
• Utilizing the pair distribution function, obtainable from equilibrium statistical mechanics.
• Comparison of calculated self-diffusion coefficients with molecular dynamics simulation data.

Main Results:

• Good agreement between the kinetic theory calculations and molecular dynamics simulations was achieved, particularly at high densities.
• The study highlights the significant contributions of potential of mean force and local correlations to transport coefficients.
• The new method overcomes limitations of free-volume theory concerning long-range potentials.

Conclusions:

• The mean force kinetic theory provides a robust method for calculating self-diffusion in dense supercritical Lennard-Jones fluids.
• This approach is expected to be applicable to a broader range of systems, including plasma and electrolyte mixtures.