Calculating Thermodynamic Factors for Diffusion Using the Continuous Fractional Component Monte Carlo Method

Area of Science:

• Thermodynamics
• Chemical Engineering
• Computational Chemistry

Background:

• Thermodynamic factors link Fick and Maxwell-Stefan diffusion coefficients for mass transfer.
• Indirect methods for determining thermodynamic factors depend on model accuracy.
• Direct molecular insertion methods like Permuted Widom's Test Particle Insertion (PWTPI) fail in dense systems.

Purpose of the Study:

• To introduce and validate the Continuous Fractional Component Monte Carlo (CFCMC) method for direct thermodynamic factor calculation.
• To overcome the limitations of existing methods in dense and complex molecular systems.
• To provide a robust computational tool for mass transfer studies.

Main Methods:

• Utilized the Continuous Fractional Component Monte Carlo (CFCMC) method, adapting the Permuted Widom's Test Particle Insertion (PWTPI) approach.
• Employed fractional molecules with modulated interactions via a coupling parameter for efficient insertions/removals.
• Applied the method to binary Lennard-Jones, ternary Weeks-Chandler-Andersen, and realistic CO2/H2 mixtures.

Main Results:

• CFCMC demonstrated excellent agreement with PWTPI for ideal molecular systems.
• Calculations for CO2/H2 mixtures showed strong concordance with the NIST REFPROP database.
• The CFCMC method proved effective even in highly dense systems, overcoming prior limitations.

Conclusions:

• CFCMC is a highly effective method for directly calculating thermodynamic factors in diffusion.
• The method is robust for both simple and complex, dense molecular systems.
• CFCMC offers a reliable computational approach for mass transfer research.