GROWTH-RATE DISPERSION IN SMALL CRYSTALS AND ITS RELATION TO MOSAIC SPREAD
GROWTH-RATE DISPERSION IN SMALL CRYSTALS AND ITS RELATION TO MOSAIC SPREAD
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DOI：
10.1016/0022-0248(92)90597-c
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发表时间：
1992-10-01
影响因子：
1.8
通讯作者：
DAVEY, RJ
中科院分区：
文献类型：
--
作者：
HARDING, MM;RULE, RJ;DAVEY, RJ
高镶嵌扩展是许多复杂材料（例如某些沸石和蛋白质）的共同特征，对于这些材料，禁止制备大单晶。在之前的一项系统研究中，发现非常小的氯酸钠晶体的生长速率和马赛克扩展之间存在直接相关性。这项工作试图通过将测量扩展到更广泛的简单材料来探索这种效应的普遍性。在水溶液中二次成核产生的磷酸二氢铵（ADP）、氯酸钠和蔗糖的小晶体（5-200 μ m）已在恒定的过饱和条件下生长。使用光学显微镜观察到每种材料的生长速率的广泛分散。从溶液中成功地回收了许多已知生长速率的单个晶体，并在达雷斯伯里实验室使用同步辐射劳厄衍射对每个晶体的镶嵌扩展进行了评估。所有晶体都产生包含小而尖锐的斑点的衍射图案，表明马赛克分布较低（< 0.5度）。没有相关性，发现这些相对简单的结构之间的增长速度和马赛克蔓延。此外，蔗糖的单个晶体也在溶液中产生后立即进行了检查，随后在恒定的过饱和度下生长。在生长之前和之后获得的每种晶体的劳厄图案都表现出低的镶嵌扩展，但是每种晶体以不同的速率生长。有人建议，辐射损伤可以解释先前公布的差异，并计算可接受的辐射剂量，以确定这些材料中的镶嵌扩展。
High mosaic spread is a common feature of a number of complex materials (such as certain zeolites and proteins) for which the preparation of large single crystals is prohibited. In one previous systematic study, a direct correlation between growth rate and mosaic spread was found for very small crystals of sodium chlorate. This work has attempted to explore the generality of the effect by extending measurements to a wider range of simple materials. Small crystals (5-200 mum) of ammonium dihydrogen phosphate (ADP), sodium chlorate and sucrose, generated by secondary nucleation in aqueous solution, have been grown under constant conditions of supersaturation. A wide dispersion of growth rates was observed for each material using optical microscopy. A number of individual crystals of known growth rate were successfully retrieved from solution and an assessment of the mosaic spread of each crystal was made using synchrotron radiation Laue diffraction at Daresbury Laboratory. All of the crystals produced diffraction patterns comprising small, sharp spots, indicative of low mosaic spread ( < 0.5-degrees). No correlation was found between growth rate and mosaic spread for these relatively simple structures. In addition, individual crystals of sucrose have also been examined immediately after creation in solution and subsequently grown-on at constant supersaturation. The Laue patterns obtained for each crystal, both before and after growth, exhibited low mosaic spread, yet each crystal grew at a different rate. It is suggested that radiation damage can account for the previously published discrepancies, and acceptable radiation doses are calculated for the determination of mosaic spread in these materials.