Fick Diffusion Coefficient Matrix of a Quaternary Liquid Mixture by Molecular Dynamics

Area of Science:

• Physical Chemistry
• Chemical Engineering
• Materials Science

Background:

• Understanding multicomponent diffusion is crucial for chemical processes.
• Predicting diffusion in complex liquid mixtures remains challenging.
• Existing methods often lack accuracy for quaternary systems.

Purpose of the Study:

• To consistently sample the Fick diffusion coefficient matrix of a quaternary liquid mixture using molecular dynamics.
• To determine phenomenological diffusion coefficients and thermodynamic factors.
• To propose a system size correction methodology for multicomponent mixtures.

Main Methods:

• Molecular dynamics (MD) simulations were employed.
• The Green-Kubo formalism and Kirkwood-Buff theory were utilized.
• System size correction was applied to Fick diffusion coefficients.

Main Results:

• The Fick diffusion coefficient matrix for water + methanol + ethanol + 2-propanol was successfully sampled.
• Significant composition dependence and cross-coupling effects were observed, particularly impacting water diffusion.
• Radial distribution functions provided insights into intermolecular interactions and coupling effects.

Conclusions:

• Molecular dynamics simulations can reliably predict Fick diffusion coefficients in quaternary mixtures.
• Hydrogen bonding significantly influences diffusion behavior and coupling effects.
• This work represents a significant advancement in understanding multicomponent diffusion.