Alternative algorithms for simultaneous modeling of ordering and intermediate compound growth during reactive diffusion

Abstract

Abstract Standard Monte Carlo algorithms with constant pair interactions within the first coordination shell are usually quite effective for the description of ordering, tracer diffusion, chemical diffusion (but without Kirkendall shift effect) within any already existing ordered intermediate phase. Yet, one encounters big problems if one tries to simulate the formation and growth of ordered intermediate phase or, especially, simultaneous formation and growth of several intermediate phases during interdiffusion. Two algorithms providing solution of this problem, are discussed. The first algorithm is known (but not widely used for reactive growth) – account of interactions in the two coordination shells with negative mixing energy in the first coordination shell and positive mixing energy in the second one. The second algorithm is new: interactions only within the first coordination shell of each atom but depending on the local composition within the cluster around interacting atoms. Both algorithms are shown to provide formation and growth of the ordered intermediate phases with rather narrow concentration ranges, growing with time (after some initial period) according to parabolic law.