Multiple Free Energy Calculations from Single State Point Continuous Fractional Component Monte Carlo Simulation...

Area of Science:

• Computational Chemistry
• Thermodynamics
• Statistical Mechanics

Background:

• Free energy calculations are crucial for understanding chemical systems.
• Traditional methods often require numerous simulations at different conditions.
• Accurate computation of chemical potential is essential for mixture behavior prediction.

Purpose of the Study:

• To introduce an efficient method for free energy calculations of mixtures.
• To enable computation of chemical potential at multiple temperatures and pressures from a single simulation.
• To reduce the computational burden of free energy calculations.

Main Methods:

• Combining umbrella sampling and continuous fractional component Monte Carlo.
• Performing a single simulation at a reference state.
• Extrapolating chemical potential to nearby thermodynamic conditions.

Main Results:

• Accurate chemical potential estimates obtained without postprocessing.
• Demonstrated applicability to Lennard-Jones systems and realistic mixtures (methanol, ammonia-nitrogen-hydrogen).
• Partial molar volumes and enthalpies derived directly from chemical potentials.

Conclusions:

• The proposed method offers a significant reduction in simulations needed for free energy calculations.
• It provides direct access to thermodynamic properties like partial molar volumes and enthalpies.
• The method's accuracy is validated for various systems and conditions, with limitations noted for large systems and nonlinear potential variations.