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Rare event dynamics and reaction rates

Many processes in chemical and biological systems such as chemical reactions, conformational changes of macromolecules, nucleation processes in solution or in other condensed phases take place by infrequent fluctuations of the locations of the molecules in the solvent and the reactive system. Capturing these special fluctuations that finally determine the mechanism and rate of the process is a challenging problem in computations. This problem lies at the heart of chemistry. While microscopic expressions for rate constants are well known, their computation presents challenges for simulations since the reactive events often occur rarely, and the long time scales that are typical for reactive processes are not accessible using simple molecular dynamics methods. Furthermore, the underlying free energy surface is very complex with many saddle points that prevent sampling of possible reaction pathways. As a result, the reaction coordinate may be a complex many-body function of the system's degrees of freedom. Since there is not an a priori way to define a "good" reaction coordinate, methods are being developed to assist in a systematic construction of a reaction coordinate.

One of the major advances that we have achieved in our lab, is to transfer our knowledge on rare event dynamics and activated processes in a new realm of processes: the study of disintegration mechanisms of charged droplets. In the charged nanodroplets the activated processes is a central theme in their fragmentation mechanisms, release of macromolecular ions from droplets and the chemical reactions that happen within the droplet.

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