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

Abstract

Using DMol and the discrete variational method within the framework of the 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 agrees with the 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 the 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 atoms 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 the NiAl alloy.