Elucidation of the crystal structure of oxyapatite by high-resolution electron microscopy.
Elucidation of the crystal structure of oxyapatite by high-resolution electron microscopy.
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通过高分辨率电子显微镜阐明氧磷灰石的晶体结构。
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发表时间：
1999
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通讯作者：
Lidin
中科院分区：
文献类型：
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作者：
Alberius Henning P;Landa;Larsson;Lidin
不同羟基磷灰石（OHAp）样品的高分辨率电子显微镜（HREM）图像显示沿[001]的p3投影对称，而不是与OHAp的P6_3/m空间群相容的p6投影对称。图像处理被用来明确地建立三重对称沿图像主导[001]。在透射电镜下观察到OHAp晶体的分解，并得出三重对称的结论，这对应于分解过程的早期步骤，即OHAp脱水为氧化磷灰石（OAp）。在OAp中沿6(3)轴每1秒移除1个O原子的结构模型具有最大的空间群对称性P{ar 6}。这与观察到的p3投影对称性是一致的。利用HREM图像和原子结构的几何优化估计了该OAp模型与OHAp结构相比的原子位移。虽然无法根据衍射数据对原子坐标进行修正，但该模型的模拟HREM图像与实验图像吻合较好。
High-resolution electron-microscopy (HREM) images from different hydroxyapatite (OHAp) samples showed p3 projection symmetry along [001] instead of the p6 projection symmetry compatible with the space group P6_3/m of OHAp. Image processing was used to establish without ambiguity that threefold symmetry dominates the images along [001]. OHAp crystals decompose in the transmission electron microscope and it is concluded that the threefold symmetry observed corresponds to an early step in the decomposition process, the dehydration of OHAp to oxyapatite (OAp). A structural model for OAp where every second O atom along the 6(3) axis in OHAp is removed has the maximal space-group symmetry P{ar 6}. This is compatible with the p3 projection symmetry observed. Atomic shifts in this OAp model compared to the OHAp structure were estimated using the HREM images and geometric optimizations of the atomic structure. No refinements of the atomic coordinates against diffraction data were possible but the simulated HREM images of this crude model fit well with the experimental images.