Free energy barriers from biased molecular dynamics simulations

Area of Science:

• Computational Chemistry
• Chemical Physics
• Materials Science

Background:

• Atomistic simulations quantify free energies using collective variables (CVs) to generate free energy surfaces (FES).
• Standard FES methods capture metastable state stability but fail to consistently compute transition state barrier heights due to CV dependence.
• Inconsistent free energy barriers hinder accurate kinetic predictions in chemical and physical processes.

Purpose of the Study:

• To present a simple gauge correction method for consistent free energy barrier calculations.
• To enable accurate computation of transition state barriers from atomistic simulations.
• To improve the reliability of free energy-based kinetic descriptions.

Main Methods:

• Developed a gauge correction procedure to eliminate inconsistencies in FES.
• Utilized reweighting techniques on existing simulated trajectories to obtain both standard and gauge-corrected FES.
• Applied the method to diverse systems: particle in Lennard-Jones fluid, Diels-Alder reaction, and sodium crystallization.

Main Results:

• The gauge correction method successfully produced consistent free energy barriers across different systems.
• Demonstrated accurate capture of chemical and physical transformation kinetics.
• Showcased that FES can be converged on short timescales (sub-nanoseconds).

Conclusions:

• The gauge correction approach provides a robust way to compute reliable free energy barriers.
• This method enhances the utility of FES for studying reaction kinetics, especially at higher levels of theory.
• The technique offers a cost-effective way to improve the accuracy of atomistic simulations for predicting transformation dynamics.