Time: 03:20 p.m.
Place: ICAMS² 2013, International Colloquium on Advanced Materials Simulation, Bochum, Germany
Modelling the dynamical evolution of systems on the atomistic level over extended time scales is a particularly challenging task. If the dynamics are governed by so-called rare events then the time scales of interest cannot be reached with regular molecular dynamics simulations. A number of methods have been developed to model the dynamics of rare events; the method of choice depends on the problem at hand. Here, several approaches and their application to diffusion, segregation and phase transformation kinetics are discussed.
The diffusion and segregation of interstitial and substitutional point defects can often be modelled within a lattice kinetic Monte Carlo approach combined with highly accurate density-functional theory calculations. Solid-solid phase transformations, on the other hand, might involve massive structural rearrangements including concerted multi-atom processes. To investigate such processes at interfaces between cubic and topologically close-packed phases in transition metals we employ adaptive kinetic Monte Carlo. These simulations are computationally much more demanding than lattice-based Monte Carlo and require an efficient but still accurate description of interatomic interactions in the different phases. In solid-liquid phase transformations the interface mobility is often relatively high, but to follow the full transformation from the solid to the liquid phase or vice versa a high nucleation barrier has to be overcome. To investigate dynamical trajectories connecting the solid and liquid state we use transition path sampling. A proper reweighting of the path ensemble allows not only for the extraction of free energy barriers but also for the analysis of dynamical properties and transformation mechanisms.