Self-diffusion coefficient of the square-well fluid from molecular dynamics simulations within the constant force...

Area of Science:

• Thermodynamics
• Computational Physics
• Fluid Dynamics

Background:

• The self-diffusion coefficient is a crucial transport property for understanding fluid behavior.
• Accurate modeling of particle interactions, like the square-well potential, is essential for predicting transport properties.
• Supercritical fluid states present unique challenges for theoretical and simulation-based studies.

Purpose of the Study:

• To systematically investigate the self-diffusion coefficient of square-well fluids using molecular dynamics simulations.
• To analyze the influence of the square-well potential range (λ) on self-diffusion.
• To validate simulation results against theoretical predictions like the Enskog method.

Main Methods:

• Molecular dynamics (MD) simulations were performed in the canonical (N, V, T) ensemble.
• The constant force approximation was employed to model the discrete square-well potential.
• Simulations covered various fluid densities at supercritical thermodynamic states for λ values between 1.1 and 1.5.

Main Results:

• The self-diffusion coefficient was found to be highly sensitive to the square-well potential range (λ).
• Simulation results demonstrated good agreement with predictions from the Enskog method.
• The computed self-diffusion coefficient multiplied by density showed excellent extrapolation to the zero-density limit from Chapman-Enskog theory.

Conclusions:

• The constant force approximation is an effective method for calculating transport properties of square-well fluids via MD simulations.
• The study provides valuable data for refining theoretical models, including the Enskog method.
• Understanding the impact of potential range on diffusion is key for accurate fluid modeling.