Local Diffusion Coefficients in Spherically Symmetric Systems Using the Smoluchowski Equation and Molecular Dynamics

Area of Science:

• Physical Chemistry
• Computational Chemistry

Background:

• Accurate estimation of local self-diffusion coefficients is vital for understanding interfacial systems.
• Spherical interfacial systems are common in nature, influencing processes like atmospheric partitioning and biological transport.

Purpose of the Study:

• To extend a method for estimating local diffusion coefficients from flat to spherically symmetric interfaces.
• To provide an accurate and validated computational approach for analyzing diffusion in spherical systems.

Main Methods:

• Derived an analytical solution to the linearized Smoluchowski equation in spherical coordinates.
• Utilized molecular dynamics simulations to obtain necessary parameters.
• Validated the solution against numerical solutions and experimental data for SPC/E water.

Main Results:

• The derived analytical solution accurately estimates local self-diffusion coefficients in spherical systems.
• The method was validated in bulk SPC/E water and applied to a water droplet in vapor.
• Observed an increase in diffusion coefficient from the droplet center to the interface.

Conclusions:

• The developed method provides a reliable tool for studying diffusion in spherical interfacial systems.
• The findings are consistent with previous studies on flat interfaces, confirming the method's applicability.
• This research enhances our understanding of molecular transport in complex, naturally occurring systems.