Theoretical investigation of the interaction of oxygen with pure and K-doped NiTi shape memory surface alloys Original Research Article

Density functional based theories and experiments agree well on the value of the heat of formation of TiO2 on NiTi surfaces. However, experimental studies of polycrystalline NiTi surfaces tend to indicate that Ti atoms are always abundantly available at the surface. This theoretical study indicates that whether Ti atoms are dominantly available at the surface depends on the surface index. On NiTi(001) in the B2 phase, the surface can be Ti or Ni terminated, with equal probability, while on NiTi(110) in the B2 phase and NiTi(010) in the B19ʼ phase, Ti atoms are favored to be present at the surface.