Understanding dislocation slip in stoichiometric rocksalt transition metal carbides and nitrides

The slip systems for B1MXcompounds (M= Ti, Zr, Hf, V, Nb, Ta and X= C, N) have been studied extensively both experimentally and computationally as they influence the materials mechanical behavior at both high and low temperatures. Despite many investigations, the differences in observed slip systems, either {111} or {110}, in these materials remain an open question. In this paper, the factors that may determine the slip preference of these compounds have been studied based on the results from first principle calculations. The generalized stacking fault surfaces for all of the materials were computed and used to provide a more comprehensive understanding of slip plane choices. Through analysis of this data, it is found that among different indicators of slip, the normalized splitting width and the intrinsic stacking fault energy are the most useful indicators of the choice of slip planes in these materials. In addition, these indicators of slip are controlled by the structural energy differences between the B1 and tungsten carbides structures, which are correlated well with the number of valence electrons.