First-principles calculations were made of the structural and electronic properties of the orthorhombic phase. The energies which were deduced from these calculations were used in a statistical mechanics model, and the results showed that the preferred constituent defects in non-stoichiometric material were 8d Ni antisites on the Ni-rich side and Ni vacancies on the Al-rich side.

Electronic Structure and Thermodynamics of Defects in NiAl3. M.Rasamny, M.Weinert, G.W.Fernando, R.E.Watson: Physical Review B, 2001, 64[14], 144107 (8pp)