The usefulness of atomistic simulations is generally hampered by the presence of several metastable states separated by high barriers leading to kinetic bottlenecks. Transitions between metastable states thus occur on much longer time scales than one can simulate. Numerous enhanced sampling methods have been introduced to alleviate this time scale problem, including methods based on identifying a few crucial order parameters corresponding to the relevant slow degrees of freedom and enhancing their sampling through the introduction of an external biasing potential .
Here we will discuss Variationally Enhanced Sampling , a generally applicable enhanced sampling method where an external bias potential is constructed by minimizing a convex functional. We present numerous examples from physics, chemistry, and materials science which show the flexibility and practicality of the method [3-6]. We will furthermore show how the variational property of the method can be used to extend the method in various innovative ways, e.g.: to obtain kinetic information from atomistic simulation ; to accelerate nucleation events by employing models from classical nucleation theory ; to parameterize coarse-grained phenomenological models from microscopic simulations ; and to incorporate experimental information into molecular simulations.
We will also introduce the VES code , an open-source library for the PLUMED 2 plugin that implements methods based on Variationally Enhanced Sampling.
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