A theoretical and experimental study of lead substitution in calcium hydroxyapatite

D. E. Ellis*, Joice Terra, O. Warschkow, M. Jiang, Gabriela B. González, J. S. Okasinski, M. J. Bedzyk, Alexandre M. Rossi, Jean Guillaume Eon

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

63 Scopus citations

Abstract

Characterization of lead substitution for calcium in hydroxyapatite (CaHA) is carried out, using experimental techniques and Density Functional theoretical (DFT) analyses. Theoretical modeling is used to obtain information of the Pb chemical environment for occupancy at either Ca(I) or Ca(II) sites of CaHA. Effects of the larger ionic radius of Pb+2 compared to Ca +2 are apparent in embedded cluster calculations of local chemical bonding properties. DFT periodic planewave pseudopotential studies are used to provide first-principles predictions of local structural relaxation and site preference for PbxCa10-xHA over the composition range x ≤ 6. General characteristics of the polycrystalline material are verified by X-ray diffraction and FTIR analysis, showing the presence of a single phase of CaHA structure. A short range structure around lead is proposed in order to interpret the Pb L-edge EXAFS spectrum of the solid solution Ca 6.6Pb3.4HA. In this concentration we observe that lead mainly occupies Ca(II) sites; the EXAFS fit slightly favors Pb clustering, while theory indicates the importance of Pb-Pb avoidance on site (II).

Original languageEnglish (US)
Pages (from-to)967-976
Number of pages10
JournalPhysical Chemistry Chemical Physics
Volume8
Issue number8
DOIs
StatePublished - Feb 27 2006

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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