Measurement of three-dimensional intensity data in electron diffraction by the precession technique
Measurement of three-dimensional intensity data in electron diffraction by the precession technique
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DOI：
10.1016/s0304-3991(98)00038-2
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发表时间：
1998-08-01
期刊：
影响因子：
2.2
通讯作者：
Gjonnes, J
中科院分区：
文献类型：
--
作者：
Berg, BS;Hansen, V;Gjonnes, J
最近由布里斯托尔大学的文森特和米德格利设计的进动技术已经被用来获得足够质量的三维强度数据，用于确定金属间化合物相AlmFe的结构。使用进动方法有效地减少了动力学相互作用，并且强度数据可以在运动学近似下处理。来自总共8个投影的衍射图被耦合到图像分析系统的CCD相机数字化，并且通过组合来自不同投影的等效反射，强度数据通过基于每个投影共同的反射之间的实验强度比的最小二乘法被合并到三维数据集。对于计算Patterson图以及最终的傅立叶图，需要强度数据的PI三维集合作为结构模型的指南。讨论了定量数据的质量以及影响方法和计算的因素。初步结论是，强度有望用于计算帕特森和傅立叶映射，但对于最小二乘精化则不太有用。(C)1998 Elsevier Science B.V.保留所有权利。
The precession technique, recently devised by Vincent and Midgley at the University of Bristol, has been used to acquire three-dimensional intensity data of sufficient quality for structure determination of the intermetallic phase AlmFe. Dynamical interactions are effectively reduced using the precession method, and the intensity data can be treated within a kinematical approximation. Diffraction patterns from a total of eight projections were digitised by a CCD camera coupled to an image analysis system, and by combining equivalent reflections from different projections, the intensity data was merged into a three-dimensional data set by a least-squares procedure based on experimental intensity ratios between reflections common to each projection. PI three-dimensional set of intensity data is needed for calculations of Patterson maps, and eventually Fourier maps, as a guide for a structure model. The quality of the quantitative data and the factors affecting the methods and calculations are discussed. The preliminary conclusion is that the intensities are expected to be useful for calculating Patterson and Fourier maps, but less so for least-squares refinement. (C) 1998 Elsevier Science B.V. All rights reserved.