Optimizing potentials for a liquid mixture: a new force field for a tert-butanol and water solution

Area of Science:

• Computational chemistry and condensed-phase physics.
• Development of simulation methodologies.
• Thermodynamics and statistical mechanics of liquid mixtures.

Background:

• Accurate potential parameters are crucial for reliable condensed-phase simulations.
• Direct calculation of macroscopic observable derivatives offers a novel optimization approach.
• Existing methods may lack robustness or accuracy in parameter optimization.

Purpose of the Study:

• To introduce and validate a new technology for optimizing potential parameters in condensed-phase simulations (POP).
• To demonstrate the effectiveness of direct derivative calculations and Newton trust region protocols.
• To accurately model the phase behavior and Kirkwood Buff integrals of the tert-butanol/water mixture.

Main Methods:

• Direct calculation of macroscopic observable derivatives with respect to potential parameters.
• Application of a local minimization scheme comparing simulated and experimental data.
• Utilizing the Newton trust region protocol for enhanced optimization accuracy and robustness.

Main Results:

• Successful optimization of potential parameters for the tert-butanol/water liquid mixture after four iterations.
• Accurate prediction of the mixture's phase behavior.
• Precise determination of Kirkwood Buff (KB) integrals, validating the POP technology.
• Demonstration that potentials derived solely from KB integrals or pair correlation functions are not unique.

Conclusions:

• The developed POP technology provides an accurate and robust method for optimizing potential parameters in condensed-phase simulations.
• The Newton trust region protocol significantly improves optimization efficiency and reliability.
• The study highlights the importance of comprehensive data for unique potential determination, even when using KB integrals.