Lunin Vladimir Y
Institute of Mathematical Problems of Biology, Russian Academy of Sciences, Pushchino, Moscow Region 142290, Russian Federation.
Acta Crystallogr D Biol Crystallogr. 2012 Jun;68(Pt 6):732-4. doi: 10.1107/S0907444912011420. Epub 2012 May 17.
A number of methods to detect twinning are based upon the assumption that the statistical properties of diffracted intensities are different for twinned and untwinned specimens. This may not be true for a large portion of the reflections in a twinned specimen if a noncrystallographic screw axis parallel to the twinning axis is present. In this case, up to half of all reflections can obey Wilson statistics, which are typical of untwinned crystals. The distribution corresponding to a whole set of observed intensities is biased towards the Wilson distribution in this case.
许多检测孪晶的方法是基于这样一种假设，即孪晶和非孪晶晶样衍射强度的统计特性不同。如果存在与孪晶轴平行的非晶体学螺旋轴，那么对于孪晶晶样中的大部分反射来说，情况可能并非如此。在这种情况下，所有反射中多达一半可以符合威尔逊统计，这是未孪晶晶体的典型特征。在这种情况下，对应于一整套观测强度的分布会偏向威尔逊分布。
