Saddle Point Energies from Ab Initio Jump Profiles in MC Simulation of Order Kinetics in Intermetallics.
Kinetic Monte Carlo (KMC) simulation is a valuable tool to investigate conﬁgu-ration changes in intermetallic compounds. The elementary process is the jump of an atomfrom a lattice site to a neighboring vacancy. In classical transition state theory the jump ratecontains the energy diﬀerence between the original equilibrium state and the saddle point (=transition) state. In traditional KMC the saddle point has mostly received rather careless treat-ment, setting it constant or relating it to the type of jumping atom. In the present work, saddlepoint heights were considered explicitly. Taking L12 ordered Ni3Al as an example, jump energyproﬁles for various atom environments were calculated ab initio in relaxed conﬁgurations ofa 3x3x3 supercell, employing the Nudged Elastic Band method where necessary. From theseresults, eﬀective ’pure’ saddle point heights were extracted. To show the eﬀect on kinetics,simulations of order-order transitions were done with jump probabilities based on these results.When compared to the old assumption of constant saddle point heights, both overall kineticsand detailed jump statistics result considerably changed.
Yves Bréchet, Emmanuel Clouet, Alexis Deschamps, Alphonse Finel and Frédéric Soisson
M. Leitner et al., "Saddle Point Energies from Ab Initio Jump Profiles in MC Simulation of Order Kinetics in Intermetallics.", Solid State Phenomena, Vols. 172-174, pp. 1022-1027, 2011