On the composition and atomic arrangement of calcium-deficient hydroxyapatite: An ab-initio analysis
On the composition and atomic arrangement of calcium-deficient hydroxyapatite: An ab-initio analysis
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DOI：
10.1016/j.jssc.2008.03.035
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发表时间：
2008-08
影响因子：
3.3
通讯作者：
D. Zahn;O. Hochrein
中科院分区：
文献类型：
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作者：
D. Zahn;O. Hochrein
本文对缺钙羟基磷灰石中的缺陷星座进行了系统的研究。沿着这条线，我们探索不同的安排，电荷补偿，包括阳离子空位和替代缺陷。整体缺陷星座由阴离子的不同质子亲和力或与空位形成相关的能量成本以及库仑能量的最小化（这意味着阴离子和阳离子缺陷的小距离）两者支配。根据缺钙部位的类型，这会导致两种特定的缺损排列。其中，嵌入羟基磷灰石OH−离子的三角形钙离子最有可能缺乏。由此产生的电荷通过缺钙三角形内的OH−离子的质子化和空位钙位置最近邻的PO 43 −离子的质子化来补偿。这种星座的强烈能量偏好表明，常用的化学式Ca 10 −x（HPO 4）x（PO 4）6−x（OH）2−x（H2O）x（0<x <$1）反映了缺钙羟基磷灰石的合理近似组成。
A systematic study of defect constellations in calcium-deficient hydroxyapatite is reported. Along this line, we explore different arrangements for charge compensation, including cationic vacancies and substitutional defects. The overall defect constellation is governed by both the different proton affinity of the anions or energy costs related to vacancy formation and minimization of the Coulomb energy which implies small distances of the anionic and cationic defects. Depending on the type of the calcium-deficient site, this gives rise to two specific defect arrangements. Among these, the calcium ions forming triangles which embed the OH−ions of hydroxyapatite are most likely to be deficient. The resulting charge is compensated by protonation of the OH−ion within the deficient calcium-triangle and protonation of a PO43−ion in the nearest neighbourhood of the vacant calcium site. The strong energetic favouring of such constellations indicates that the commonly used chemical formulae Ca10−x(HPO4)x(PO4)6−x(OH)2−x(H2O)x(0<x⩽1) reflect a reasonable approximation of the composition of calcium-deficient hydroxyapatite.