Partial structural information combined with the tangent formula for noncentrosymmetric crystals
Partial structural information combined with the tangent formula for noncentrosymmetric crystals
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非中心对称晶体的部分结构信息与正切公式相结合
DOI：
10.1107/s0567740868001925
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发表时间：
1968
期刊：
影响因子：
--
通讯作者：
J. Karle
中科院分区：
文献类型：
--
作者：
J. Karle
方法正切公式为（Karle & Hauptman, 1956） Z [F~ Eh_kl sin (~ 0k”~~ Oh—k)(1) tan~ 0h= X [F~ Eh_]。kl COS (~ 0k+~ 0h_k)'，其中~ oh是与归一化结构因子Eh相关的相。很明显，为了应用(1)，需要知道一些初始相。对已知的对（~ 0k,~ Oh_k）进行求和，并且已经观察到，只要[Eh [， IF~]和]Eh-k]是最大的数量级，就可以从相对较少的求和贡献中获得良好的精度（Karle & Karle, 1966）。这里感兴趣的问题是能否在最大的[E]值之间获得足够精确的一组初始相
Method The tangent formula is (Karle & Hauptman, 1956) Z [F~ Eh_kl sin (~ 0k"~~ Oh--k)(1) tan~ 0h= X [F~ Eh_. kl COS (~ 0k+~ 0h_k)'where~ oh is the phase associated with the normalized structure factor Eh. It is apparent that in order to apply (1) some initial phases need to be known. The sum is carried out over the known pairs (~ 0k,~ Oh_k) and it has been observed that good accuracy is obtained from relatively few contributors to the sum so long as the [Eh [, IF~] and] Eh-k] are among the largest magnitudes (Karle & Karle, 1966). The question of interest here is whether a sufficiently accurate set of preliminary phases among the largest [E [values could be obtained