Escorted Free Energy Simulations: Improving Convergence by Reducing Dissipation

TL;DR

This paper introduces a method to enhance the convergence of nonequilibrium free energy calculations by employing an artificial flow field that guides the system along near-equilibrium paths, reducing dissipation.

Contribution

The authors propose a novel approach using an artificial flow field to generate trajectories with less dissipation, improving free energy estimate accuracy and convergence.

Findings

Reduced dissipation leads to faster convergence of free energy estimates.

The method is demonstrated on a model system showing improved accuracy.

The approach is broadly applicable to various nonequilibrium simulations.

Abstract

Nonequilibrium, ``fast switching'' estimates of equilibrium free energy differences, Delta F, are often plagued by poor convergence due to dissipation. We propose a method to improve these estimates by generating trajectories with reduced dissipation. Introducing an artificial flow field that couples the system coordinates to the external parameter driving the simulation, we derive an identity for Delta F in terms of the resulting trajectories. When the flow field effectively escorts the system along a near-equilibrium path, the free energy estimate converges efficiently and accurately. We illustrate our method on a model system, and discuss the general applicability of our approach.