Molecular simulation of loading dependent slow diffusion in confined systems.

Area of Science:

• Physical Chemistry
• Materials Science
• Chemical Engineering

Background:

• Calculating the diffusivity of adsorbed molecules in confined systems is crucial for understanding various chemical and physical processes.
• Traditional methods like molecular dynamics simulations have limitations in terms of accessible time scales and molecule types.
• Transition state theory provides a framework for studying reaction rates but needs extension for quantitative diffusivity calculations in complex systems.

Purpose of the Study:

• To develop an extension of transition state theory for quantitatively computing the diffusivity of adsorbed molecules.
• To enable accurate diffusivity calculations in confined systems, even at non-zero loading conditions.
• To overcome the limitations of molecular dynamics in terms of accessible time scales and molecular complexity.

Main Methods:

• An extension to traditional transition state theory was developed.
• The method was applied to compute the diffusivity of adsorbed molecules in confined systems.
• The results were compared with conventional molecular dynamics simulations.

Main Results:

• The extended transition state theory quantitatively computes diffusivity in confined systems at non-zero loading.
• The computed diffusivities show excellent agreement with molecular dynamics simulation results.
• The approach significantly extends the range of accessible time scales compared to molecular dynamics.

Conclusions:

• The developed extension of transition state theory is a powerful tool for calculating molecular diffusivity in confined systems.
• This method overcomes the time scale limitations of molecular dynamics, making it applicable to a wider range of systems and molecules.
• The approach is versatile and can be applied to any system with free energy barriers and any guest molecule type.