Optimizing the switching function for nonequilibrium free-energy calculations: an on-the-fly approach

Area of Science:

• Computational physics
• Chemical physics
• Statistical mechanics

Background:

• Nonequilibrium switching simulations are popular for free-energy calculations since Jarzynski's identity.
• Simulation efficiency hinges on selecting an optimal switching function to minimize work and computational cost.

Purpose of the Study:

• To present a novel method for estimating efficient switching functions during nonequilibrium free-energy simulations.
• To determine the switching rate on-the-fly, eliminating the need for trial pulls.

Main Methods:

• Developed an on-the-fly method to estimate switching functions based on fictitious force fluctuations and relaxation time.
• Integrated the method into existing nonequilibrium switching simulation frameworks.
• Applied the method to calculate free-energy differences for Einstein crystals and van der Waals gas expansion.

Main Results:

• The on-the-fly method determines the switching rate dynamically without requiring preliminary simulations.
• Demonstrated superior performance of the on-the-fly method over standard switching functions in test cases.
• Achieved significant reduction in computational cost and dissipative work.

Conclusions:

• The proposed on-the-fly method provides a more efficient and robust way to determine switching functions for free-energy simulations.
• This approach is easily adaptable to various implementations of nonequilibrium switching methods.
• The findings have broad implications for accelerating free-energy calculations in diverse physical systems.