Abstract: Equilibrium equation of point defects in Ll_2 type intermetallic compounds was established to calculate the relations of the concentration of antisite defects and vacancies and bulk composi- tion in Ni_3Al.The examination of temperature effects on the point defects cleared up the mis. understanding of the properties of the“constitutional point defects”in Ni_3Al.

Key words: intermetallic compound, Ni_3Al, vacancy, antisite defect