Regensburg 2019 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 36: Condensed-matter simulations augmented by advanced statistical methodologies (joint session DY/CPP)

DY 36.10: Talk

Wednesday, April 3, 2019, 17:45–18:00, H20

Free Energy Landscape of Phase Transitions Investigated by Enhanced Sampling over Degenerate Collective Variables — •Bin Song, Kurt Kremer, and Omar Valsson — Max Planck Institute for Polymer Research, Mainz, Germany

Phase transition events such as nucleation of atomic or molecular crystals, self-assembly of micelles etc. have been intriguing scientists not only for their underlying physical principles, but also for their potential applications. Molecular dynamic simulations are increasingly called upon to either provide the detailed mechanistic insights and to prognosticate such events that may be too expensive or slow to examine with experiments. As potential energy surface of such events are often complex and difficult to sample, free energy surface (FES) are preferred. However, FES presents its own challenge to sample when the height of barriers are higher than or comparable to the thermal energy. Enhanced sampling methods biasing on properly chosen collective variables (CVs) can help overcome these barriers. Sometimes globally defined CVs are not sufficient, and more than a few of locally defined ones are needed. The increased dimensionality of the bias potential could be another source of frustration for achieving properly sampled FES, which we would like to alleviate with our new development of Variational Enhanced Sampling (VES) in cases where the local CVs are permutationally invariant. We demonstrate the capability of the new development by sampling the phase transitions in systems of increased complexity, including Lennard-Jones clusters and liquid-solid transition in materials.