String method for the study of rare events

TLDR

The authors introduce an efficient method to compute transition pathways, free energy barriers, and transition rates in complex systems with smooth energy landscapes. The method evolves parametrized strings to the most probable transition path between metastable regions, then uses umbrella sampling along the string to compute free energy barriers and transition rates. The method is applied to Lennard-Jones cluster rearrangement and thermally induced switching of a magnetic film.

Abstract

We present a new and efficient method for computing the transition pathways, free energy barriers, and transition rates in complex systems with relatively smooth energy landscapes. The method proceeds by evolving strings, i.e. smooth curves with intrinsic parametrization whose dynamics takes them to the most probable transition path between two metastable regions in the configuration space. Free energy barriers and transition rates can then be determined by standard umbrella sampling technique around the string. Applications to Lennard-Jones cluster rearrangement and thermally induced switching of a magnetic film are presented.