Effects of X (V, W, Mo, Hf, Ta, Zr) additions on the ideal cleavage fracture of Cr2Nb: First-principles determination

The effects of the additive elements X (V, W, Mo, Hf, Ta and Zr) on the ideal cleavage fracture of the C15 Cr2Nb were investigated using the first-principles method. The brittle cleavage energy Gc and critical stress σc were calculated. The results show that V on Cr sites and X (W and Zr) on Nb sites can increase the cleavage strength of Cr2Nb, while X (W and Mo) on Cr sites and X (Mo, Ta and Hf) on Nb sites can reduce the cleavage strength of Cr2Nb. Our results are consistent with available experimental ones. We also find that the effect of the element W on the cleavage strength of Cr2Nb strongly depends on its site preference in Cr2Nb. The charge densities induced by the additive elements X were also calculated in order to reveal the origin of the effects of X on the ideal cleavage fracture of Cr2Nb.