Atomistic simulation of point defects and diffusion in B2 NiAl

We investigate self-diffusion mechanisms in NiAl using molecular statics and the embedded atom method (EAM). The activation energies of Ni and Al self-diffusion in perfectly stoichiometric NiAl are calculated for three atomic mechanisms: the mechanism of next-nearest-neighbour (NNN) vacancy jumps, the 6-jump vacancy mechanism and the 4-ring mechanism. The simulations indicate that self-diffusion in stoichiometric NiAl is dominated by the mechanism of NNN vacancy jumps. Diffusion of Al by this mechanism is likely to be slower and with a higher activation energy than diffusion of Ni. The mechanism of 6-jump cycles is slightly less favourable but still highly competitive to the NNN vacancy mechanism. The 4-ring mechanism is the least effective for both Ni and Al diffusion.