Divided Saddle Theory: A New Idea for Rate Constant Calculation.

Area of Science:

• Computational chemistry
• Chemical kinetics
• Molecular dynamics

Background:

• Calculating rare event rates is crucial in chemical processes.
• Existing methods may require specialized computational techniques.
• Free energy calculations and committor analysis are common simulation outputs.

Purpose of the Study:

• To introduce a novel theory and algorithm for calculating rare event rates.
• To provide a method that leverages standard computational techniques.
• To demonstrate the efficacy of the proposed approach on relevant chemical systems.

Main Methods:

• Developed divided saddle theory (DST) by dividing the free energy saddle region into domains.
• Defined auxiliary rate constants within these saddle domains.
• Employed reweighting techniques to obtain absolute forward and backward rates from simulation data.

Main Results:

• The DST algorithm successfully obtains rate constants from postprocessed free energy and committor data.
• The method requires only standard molecular dynamics computational techniques.
• Demonstrated DST's potential on alanine-dipeptide conformer rearrangement and barbaralane Cope reaction.

Conclusions:

• Divided saddle theory (DST) offers an accessible and effective approach for rare event rate calculations.
• The method integrates seamlessly with existing free energy and committor analysis workflows.
• DST provides a valuable tool for studying complex chemical dynamics in molecular simulations.