Electronic structure and thermodynamics of defects in NiAl3

We present first-principles calculations of the structural and electronic properties of orthorhombic NiAl3, including the intrinsic point defects. The energies obtained from these calculations are employed in a statistical mechanics model to investigate the role of NiAl3 in the Ni-Al phase diagram. Our calculations show that the preferred constituent defect mechanisms for NiAl3 off stoichiometry are the 8d Ni antisites on the Ni-rich side and Ni vacancies on the Al-rich side. The calculated free energy is in agreement with the observation that NiAl3 is a stoichiometric compound