Theoretical and experimental studies of substitution of cadmium into hydroxyapatite

• Published in: Physical chemistry chemical physics : PCCP 2010-12, Vol.12 (47), p.15490-15500
• Main Authors: TERRA, J, GONZALEZ, G. B, ROSSI, A. M, EON, J. G, ELLIS, D. E
• Format: Article
• Language: English
• Subjects: Cadmium; Cadmium - chemistry; Calcium - chemistry; Chemistry; Covalence; Density functional theory; Durapatite - chemistry; Exact sciences and technology; Fourier transforms; General and physical chemistry; Hydroxyapatite; Mathematical analysis; Models, Chemical; Occupation; Site preference (crystals); Spectroscopy, Fourier Transform Infrared; X-Ray Diffraction
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c0cp01032d

Substitution of cadmium into bulk hydroxyapatite Ca((10-x))Cd(x)(PO(4))(6)(OH)(2) (CdHA: x = 0.12, 1.3, 2.5) is studied by combining X-ray diffraction data from synchrotron radiation, Fourier transform infra-red spectroscopy (FTIR) and density functional theory (DFT) calculations. Energetic and electronic analyses are carried out for several configurations of Cd substitution for Ca at both cationic sites. Rietveld analysis shows preferential occupation of the Ca2 site by cadmium. FTIR data suggest a non-negligible covalent character of Cd-OH. The much-discussed cation site preference for substitution is determined on the basis of relaxed-lattice energetics, and interpreted in terms of chemical concepts; theory indicates that the Ca2 site is clearly favored and this preference is related to the more covalent character of this site compared to that of site 1.