TWINNING BY MEROHEDRY AND X-RAY CRYSTAL-STRUCTURE DETERMINATION
TWINNING BY MEROHEDRY AND X-RAY CRYSTAL-STRUCTURE DETERMINATION
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DOI：
10.1107/s0567739476000326
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发表时间：
1976-01-01
期刊：
影响因子：
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通讯作者：
FERRARIS, G
中科院分区：
文献类型：
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作者：
CATTI, M;FERRARIS, G
根据变异，双胞胎可以有效地分为两类。第一类：晶体的劳伊对称中包含双生运算，且双生相关反射强度相等；在这种情况下，从孪生晶体上收集的一组强度与从单晶上收集的强度是无法区分的。第二类：至少一个独立的孪生操作包含在晶格对称中，但不包含在晶体的劳厄对称中（与孪生相关的反射强度不同）；了解晶体的分数体积是解决这种结构的必要条件。本文讨论了从对一类孪生体的测量中得到的结构的解和改进。
Twins by merohedry can be usefully divided in two classes. Class I: the twin operation is contained in the Laue symmetry of the crystal and twin-related reflexions have equal intensities; in this case the set of intensities collected from a twin is indistinguishable from that collected on a single crystal. Class II: at least one of the independent twin operations is contained in the lattice symmetry but not in the Laue symmetry of the crystal (twin-related reflexions differ in intensity); a knowledge of fractional volumes of crystals is necessary to solve the structure. The solution and refinement of a structure from measurements performed on a twin of class I are discussed.