The temperature and compositional dependences of the formation of thermal vacancies in this compound were studied by means of positron lifetime spectroscopy. It was found that the effective vacancy formation enthalpy increased monotonically from 1.65 to 2.01eV upon increasing the Ni content from 74.1 to 76.5at%. The use of a model which was based upon the interaction of nearest-neighbor atoms suggested that predominant formation of thermal vacancies on the Ni sub-lattice occurred, with high concentrations of antisite atoms.

Thermal Formation of Atomic Vacancies in Ni3Al K.Badura-Gergen, H.E.Schaefer: Physical Review B, 1997, 56[6], 3032-7