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Abstract

The precipitation of complex intermetallic phases like topologically close-packed (TCP) phases in steels and single-crystal superalloys is governed by the formation of internal interfaces. A fundamental understanding of these interfaces requires insight into the bond-breaking and bond-making during atomic rearrangements. Both, the atomistic detail and the characteristic length-scale of realistic interfaces, can be captured by large-scale atomistic simulations. A key requirement to make such simulations insightful is a reliable and computationally efficient description of the interatomic interactions. We use analytic bond-order potentials (BOPs) that are derived by systematically coarse-graining the electronic structure from the density-functional theory (DFT) formalism to an intuitive tight-binding (TB) bond model and further on to the analytic BOP. The BOP provide similar accuracy as TB calculations at less computational effort and thus open the way to large-scale atomistic simulations of systems that cannot be described by classical empirical potentials.
Here, we outline the methodology of analytic BOP and demonstrate their applicability to the structural stability of TCP phases in comparison to DFT and TB. We present recently developed BOPs for W, Mo, Nb, and Ta that correspond to bandfillings usually encountered in TCP phasesand demonstrate their applicability to grain-boundaries and interfaces between TCP and cubic phases.