First-principles calculations of Zn–K XANES in Ca-deficient hydroxyapatite

Abstract

The local environment of substitutionalZn2 + inCa-deficient hydroxyapatite (HAp) was investigated using experimental and theoretical analyses ofthe x-ray absorption near edge structure (XANES). For Zn–K XANES calculations, two situations ofZn2 + were considered.One was Zn2 + substituted for Ca sites in perfect HAp, and the other was a Ca-deficient HAp model of substitutionalZn2 + associatedwith a Ca2 + vacancy charge compensated by two protons. The model ofZn2 + inperfect HAp did not reproduce the experimental Zn–K XANES spectrum. In contrast, the Ca-deficientHAp model agreed well with the experimental spectrum. This indicates that substitutionalZn2 + in Ca-deficient HApis associated with the Ca2 + vacancy complex in HAp.