Atomistic modeling of the site occupancies of Ti and Cu in NiAl

The BFS Quantum approximate method is used for calculating the energetics of NiAl alloy composed of 1024 atoms where the site occupancy preference of Ti and Cu are modelled. Thermal treatment is simulated using a Monte-Carlo-Metropolis algorithm, where pairs of atoms at nearest-neighbor distance are allowed to switch places. It is seen that the occupancy preferences respond primarily due to the weak interaction between the two alloying additions. However, various elements respond differently to changes in stoichiometry. This behavior is attributed to the strong tendency of Ti to occupy Al sites, irregardless of composition, and the correspondingly soft preference of Cu for Al or Ni sites thus leaving Cu to accommodate readily available sites.