The local environment of substitutional Zn2 + in Ca-deficient hydroxyapatite was investigated using experimental and theoretical analyses of the X-ray absorption near edge structure. For Zn–K X-ray absorption near edge structure calculations, two situations of Zn2 + were considered. One was Zn2 + substituted for Ca sites in perfect hydroxyapatite, and the other was a Ca-deficient hydroxyapatite model of substitutional Zn2 + associated with a Ca2 + vacancy charge compensated by two protons. The model of Zn2 + in perfect hydroxyapatite did not reproduce the experimental Zn–K X-ray absorption near edge structure spectrum. In contrast, the Ca-deficient hydroxyapatite model agreed well with the experimental spectrum. This indicated that substitutional Zn2 + in Ca-deficient hydroxyapatite was associated with the Ca2 + vacancy complex in hydroxyapatite.

First-Principles Calculations of Zn–K XANES in Ca-Deficient Hydroxyapatite. H.Murata, K.Shitara, I.Tanaka, A.Nakahira, T.Mizoguchi, K.Matsunaga: Journal of Physics - Condensed Matter, 2010, 22[38], 384213