DFT study of Ni segregation at the B2-NiTi(110)/rutile-TiO2(110) interface
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 TiO/NiTi interface: i) the perfect...
| Autores: | , , , , , , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión aceptada para publicación |
| Fecha de publicación: | 2019 |
| País: | España |
| Institución: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositorio: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:digital.csic.es:10261/205030 |
| Acceso en línea: | http://hdl.handle.net/10261/205030 |
| Access Level: | acceso abierto |
| Palabra clave: | Titanium dioxide DFT |
| Sumario: | 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 TiO/NiTi interface: i) the perfect interface; ii) the Ni enriched interface and iii) with oxygen vacancies in the TiO coating. We used DFT + U calculations for TiO, 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 Ti species are present at the interface, while in the bulk of the oxide layer the species is the Ti. Also, the electronic structure show that the metallic character of the alloy is unaffected by the interaction with oxygen. These results are consistent with experimental data from literature. Ni enriched interface containing O vacancies show a strong geometric distortion in the TiO layers. In all cases, Ni segregation is an a thermodynamically unfavorable process, helping to understand the biocompatibility of NiTi alloy. |
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