Effect of molecular configuration on binary diffusion coefficients of linear alkanes

Area of Science:

• Physical Chemistry
• Computational Fluid Dynamics
• Chemical Engineering

Background:

• Mass diffusion coefficients are crucial for computational combustion modeling.
• The Chapman-Enskog (CE) theory, based on gas kinetic theory, is widely used for calculating diffusion coefficients.
• CE theory assumes spherical molecular structures, limiting its applicability.

Purpose of the Study:

• To compute binary diffusion coefficients for linear alkanes using molecular dynamics simulations.
• To evaluate the accuracy of the Chapman-Enskog theory for non-spherical molecules.
• To investigate the influence of molecular shape on diffusion coefficients.

Main Methods:

• All-atom molecular dynamics simulations were employed.
• Simulations covered a temperature range of 500-1000 K.
• Molecular configurations were analyzed using radii of gyration and collision diameters.

Main Results:

• Significant discrepancies were observed between molecular dynamics results and CE theory predictions for linear alkanes.
• The CE theory's predictions were particularly inaccurate for non-spherical molecules.
• Molecular shape demonstrably affects diffusion coefficients.

Conclusions:

• The Chapman-Enskog theory, with its assumption of spherical potentials, is inadequate for accurately predicting diffusion coefficients of non-spherical molecules.
• Molecular dynamics simulations provide a more reliable method for determining diffusion coefficients in complex molecular systems.
• Accurate diffusion coefficient calculations are essential for advancing computational combustion modeling.