First-principles study of the properties of Ni/Ni 3Al interface doped with B or P

Abstract

By using a first-principles pseudopotential plane-wave method and the CASTEP program, the energetics and electronic structures as well as bonding characteristics of the Ni/Ni 3Al interface doped with B or P have been investigated. For Ni/Ni 3Al interface with a B or P atom placed at its octahedral center, fracture occurs by cleavage along the (0 0 1) atomic layer in the γ′-Ni 3Al block in a brittle manner, similar to the clean Ni/Ni 3Al interface, but its rupture strength W increases by 0.736 J/m 2 and 0.537 J/m 2, respectively. B-doping can obviously improve the local toughness of the interfacial region between the (0 0 1) atomic layer in the γ-Ni block and the coherent (0 0 2) atomic layer, i.e., region-2, whereas P-doping is deleterious for the local toughness of the interfacial regions, especially in region-1 bound by the coherent (0 0 2) atomic layer and the (0 0 1) atomic layer in the γ′-Ni 3Al block. The increase of W in the B- or P-doped systems can be attributed to the enrichment of covalent electron density between the first nearest neighbor (FNN) Ni–Al in region-1. The change of electron interactions between first nearest neighbor atoms in the interfacial regions caused by the displacement of atoms at the interfacial center octahedron is responsible for the toughening effect of B-doping and the brittle influence of P-doping on the Ni/Ni 3Al interface.