Modelagem computacional dos defeitos substitucionais na hidroxiapatita

• Autor(a) principal: Santos, Ricardo Daniel Soares
• Data de Publicação: 2014
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UFS
• Texto Completo: https://ri.ufs.br/handle/riufs/5318
• topic: Físico-química; Hidroxiapatita; Fosfato de cálcio; Metais; Metais de transição; Terras-raras; Cálcio; Simulação computacional; Calcium phosphate; Chemistry, Physical and theoretical; Earths, Rare; Hydroxylapatite; Metals; Transition metals; CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA

Hydroxyapatite - HAP compound have been widely studied due to several application. This materials approach important properties as bioactivity, biocompatibility and biofunctionality. HAP is a main biomaterials used as a ceramic material due the ability to replace bone tissue due to similar characteristics and properties to the tissue. A range of interesting application occurs when the HAP is doped. Therefore, a computer modelling, based on energy minimisation approach, was used to investigate the defects in HAP. A new set of potential parameters were fitted in order to reproduce all the experimental crystalline structure involved dopant schemes. In the next step, this potential model was used to model the intrinsic defects. According to the obtained energy, we found that pseudo-Schottky defect is more likely to occur, followed by Ca Frenkel defects. Finally, the formation of extrinsic defects induced by divalent ions, trivalent transition ions, trivalent rare-earth ions, tetravalent ions and pentavalent ions were modelled. The results show that the incorporation of the divalent ions is more likely to be substituted in the calcium site. For trivalent transition metals ions, it was found that is preferentially substitutes at the Ca compensated by interstitial oxygen. In the case of trivalent rare-earth dopant was observed that all of the trivalent rare-earth ions prefer to be incorporated in the Ca site compensated by the calcium vacancy, interstitial oxygen, phosphorus vacancy and interstitial hydroxyl,as being the more likely mechanisms. For tretavalent ions, it found an opposity behavior: Mn4+ prefers to be incorporated in the P site compensated oxygen vacancy, but in the case of ion Cr4+ has been found that the incorporation prefer be incorporated in the Ca site compensated by the hydroxyl interstitial defect. The last step, it.s found that Nb5+is preferentially substitutes at the Ca compensated by interstitial hydroxyl.