Pulling simulation predicts mixing free energy for binary mixtures.

Area of Science:

• Computational Chemistry
• Thermodynamics
• Materials Science

Background:

• Predicting mixing free energy in binary mixtures via simulations is computationally challenging.
• Accurate thermodynamic models are essential for designing and understanding mixtures.

Purpose of the Study:

• To present a novel molecular dynamics (MD) simulation method for extracting chemical potential in binary mixtures.
• To enable accurate prediction of the interaction parameter (χ) for binary mixtures.

Main Methods:

• Utilized molecular dynamics (MD) simulations with species-specific harmonic potentials to create nonuniform mole fraction profiles.
• Combined simulation results to derive the exchange chemical potential (Uex(X)).
• Fitted simulation data to free energy models to extract the interaction parameter (χ).

Main Results:

• The novel MD method successfully extracts the interaction parameter (χ) for binary mixtures.
• Results for benzene-pyridine mixtures using OPLS-AA potentials show good agreement with experimental data.
• TraPPE-UA potentials yielded results differing from experimental data, highlighting potential inaccuracies in force fields.

Conclusions:

• The developed MD simulation method provides a reliable way to calculate the interaction parameter (χ) for binary mixtures.
• Accurate molecular potentials are critical for correctly predicting mixture thermodynamic properties.
• This method offers a valuable tool for computational thermodynamics and materials design.