Energetics and electronic structure of refractory elements in the dislocation of NiAl

Using the DMol and the discrete variational method within the framework of density functional theory, we study the alloying effects of Nb, Ti, and V in the 100 (010) edge dislocation core of NiAl. We find that when Nb (Ti, V) is substituted for Al in the center-Al, the binding energy of the system reduces 3.00 eV (2.98 eV, 2.66 eV). When Nb (Ti, V) is substituted for Ni in the center-Ni, the binding energy of the system reduces only 0.47 eV (0.16 eV, 0.09 eV). This shows that Nb (Ti, V) exhibits a strong Al site preference, which is in agreement with experimental and other theoretical results. The analyses of the charge distribution, the interatomic energy and the partial density of states show that some charge accumulations appear between impurity atom and Ni atoms, and the strong bonding states are formed between impurity atom and neighbouring host atoms due mainly to the hybridization of 4d5s(3d4s) orbitals of impurity atom and 3d4s4p orbitals of host Ni atoms. The impurity induces a strong pinning effect on the 100 (010) edge dislocation motion in NiAl, which is related to the mechanical properties of NiAl alloy.