Rare event simulation

Many processes occurring in nature of technology are characterized by wide ranges of time scales. For instance, micrometer sized water droplets can remain liquid for several milliseconds down to more than 40 degrees below freezing and at higher temperatures the lifetime of undisturbed supercooled water is essentially unlimited. Thus, the time scale for the homogeneous freezing of water typically lies many orders of magnitudes beyond the picosecond time scale of basic molecular motions. Such vast separations of time scales, originating in energetic and/or entropic barriers that obstruct the motion of the system through phase space, are a challenge for the computer simulator. In the past decades one important research effort of our group was the development of trajectory base simulation methods to sampled analyze the mechanism and kinetics of rare events.

^{C. Dellago, Peter G. Bolhuis, and Phillip L. Geissler, “Transition Path Sampling”, Adv. Chem. Phys. 123, 1 (2002).
E. E. Borrero and C. Dellago, “Avoiding traps in trajectory space: metadynamics enhanced transition path sampling”, Eur. Phys. J. ST 225, 1609-1620 (2016).
G. Menzl, A. Singraber, and C. Dellago, “S-shooting: a Bennett-Chandler method for the calculation of reaction rate constants from committor trajetories”, Farad. Disc. 195, 345-364 (2016).
L. Qin, C. Dellago, and E. Kozeschnik, “An efficient method to reconstruct free energy profiles for diffusive processes in transition interface sampling simulations”, J. Chem. Phys. 150, 094114 (2019).}