DFT study of Ni segregation at the B2-NiTi(110)/rutile-TiO2(110) interface

JUAN, J.; ORAZI, V.; SANDOVAL, M.; BECHTHOLD, P.; HERNÁNDEZ-LAGUNA, A.; SAINZ-DÍAZ, C.I.; GONZÁLEZ, E.A.; JENKO, M.; JASEN, P.V.

APPLIED SURFACE SCIENCE

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2019 vol. 489 p. 287 - 296

0169-4332

NiTi alloy has important properties such as shape-memory, super-plasticity, resistance, and biocompatibility, therefore is frequently used in biomedical devices. We studied the oxidized form of this alloy and possible Ni segregation in three possible models for the TiO2/NiTi interface: i) the perfect interface; ii) the Ni enriched interface and iii) with oxygen vacancies in the TiO2 coating. We used DFT+U calculations for TiO2, because Hubbard correction encourages localization of the excess electronic charge and improves the DFT results. A standard spin polarized DFT was used for NiTi. We obtained the optimized geometries for each model and computed segregation energy, electronic structure, magnetic moment and bond order for the interface and for Ni segregation. Our calculations indicated that Ti3+ species are present at the interface, while in the bulk of the oxide layer the species is the Ti4+.