Calculation of Defect Properties of NiTi and FeTi

Abstract

The energies and configurations of interstitials and vacancies in the B2 ordered compounds NiTi and FeTi were calculated using atomistic simulation. The stable configuration of a vacancy after the removal of an Ni atom was a vacant Ni site; similarly, the removal of an Fe atom in FeTi resulted in a vacant Fe site. Removal of a Ti atom in both compounds, however, resulted in a vacant Ni or Fe site and an adjacent antisite defect. The effective vacancy formation energies in NiTi and FeTi were calculated to be 1.48 and 1.07 eV, respectively. Interstitials in NiTi formed split <111> configurations consisting of a Ni-Ni dumbbell oriented in the <111> direction with one or two adjacent antisite defects. The Fe interstitial in FeTi had a similar configuration, except the dumbbell contained Fe atoms. The Ti interstitial in FeTi formed an <110> Fe-Fe dumbbell.