Speaker: Dr. Omar Valsson, Max Planck Institute for Ploymer Research, Mainz, Germany
Title: Bridging Time Scales with Variationally Enhanced Sampling
Abstract: 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 and enhancing their sampling through the introduction of external biasing potential. Here will we discuss Variationally Enhanced Sampling (Valsson and Parrinello, PRL 113 090601, 2014), a generally applicable enhanced sampling method where an external bias potential is constructed by minimizing a convex functional. We present numerous examples from physics and chemistry which show the flexibilty and practicality of the method. We will furthermore show how the variational property of the method can be used to extend the method in various innovative ways. For example: to obtain kinetic information from atomistic simulation; to accelerate nucleation events by employing models from classical nucleation theory; and to incorporate experimental information into molecular simulations. We will also introduce the VES code (http://www.ves-code.org), an open-source library for the PLUMED 2 plugin that implements methods based on Variationally Enhanced Sampling.