Abstract:Using the first-principles plane-wave pseudopotential method based on the density functional theory, the formation and migration mechanisms of three different point defects (mono-vacancy, anti-site defect and interstitial atom) in B2-type MoTa alloy were studied. The mono-vacancy, anti-site defect and interstital atom are formed respectively from difficult to easy, acording to minimization of the formation energy. In six migration mechanisms of Mo and Ta mono-vacancies, one jump is the most favorable due to its lowest migration energies,but it will cause a disorder in the alloy. [010] one jump and [011] one jump can maintain the ordered property of the alloy but require higher migration energies,so the [010] one jump and [011] one jump should be replaced by straight [010] six jumps or bent [010] six jumps and straight [011] six jumps,respectively.