Systematic group-specific trends for point defects in bcc transition metals: An ab initio study

Density functional theory calculations have been performed to study the systematic trends of point defect behaviours in bcc transition metals. We found that in all non-magnetic bcc transition metals, the most stable self-interstitial atom (SIAs) defect configuration has the 〈1 1 1〉 symmetry. The calculated formation energy differences between the 〈1 1 0〉 dumbbell and the lowest-energy 〈1 1 1〉 configuration of metals in group 5B (V, Nb, Ta) are consistently larger than those of the corresponding element in group 6B (Cr, Mo, W). The predicted trends of SIA defects are fundamentally different from those in ferromagnetic α-Fe and correlate very well with the pronounced group-specific variation of thermally activated migration of SIAs under irradiation depending on the position of bcc metals in the periodic table.