Regensburg 2010 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 26: Poster Session
MM 26.5: Poster
Dienstag, 23. März 2010, 14:45–16:30, Poster C
Introducing variable barrier heights in Kinetic Monte-Carlo simulations: A study of order-order transitions in L12 ordered Ni3Al based on first-principles calculations — •Martin Leitner1, Doris Vogtenhuber2, Wolfgang Pfeiler1, and Wolfgang Püschl1 — 1University of Vienna, Faculty of Physics, Department Dynamics of Condensed Systems — 2University of Vienna, Faculty of Physics, Department of Computational Materials Science
Kinetic Monte-Carlo (KMC) simulation is a valuable tool when it comes to studying atom jump behavior in detail, for instance the kinetics of the long-range ordered state in intermetallics which is a precondition for a lot of favorable material properties. We introduce an improved KMC algorithm with variable saddle point heights depending on atom environment. In transition state theory the barrier height is the energy difference between the initial equilibrium state and a saddle point state which was mostly set constant in traditional treatments. In contrast, taking L12 ordered Ni3Al as a model system, an explicit calculation of the saddle point height is proposed and demonstrated. It is seen that the 4-atom window through which the jumping atom has to pass is decisive. We calculated ab initio a complete set of jump energy profiles for all possible jump types and window occupations. In KMC simulations we tested the influence of this explicit calculation and compared it to the old paradigm of constant saddle point heights. It turned out that individually computed saddle point energies make a considerable difference in jump statistics and overall kinetics.