Absolute-structure reports.
Absolute-structure reports.
复制标题
绝对结构报告。
DOI：
10.1107/s0108270113014789
复制
发表时间：
2013
期刊：
影响因子：
--
通讯作者：
H. Flack
中科院分区：
文献类型：
--
作者：
H. Flack
2011年1月至2012年11月期间发表在Acta Crystallographica Section C上的所有139个非中心对称晶体结构都被用作绝对结构报告的详细研究基础。这些结构测定涵盖了广泛的空间群，化学组成和共振散射的贡献。将A和D定义为弗里德尔对立的强度的平均值和差异，使用2AD和选择D图检查了它们的拟合水平。有人发现，无论预期的共振散射贡献的弗里德尔对立，弗里德尔差强度往往是由随机不确定性和系统误差。提供了数据收集策略的分析。据发现，导致Flack参数接近0.5的晶体结构测定可能不一定是从晶体反转孪生。Friedifstat被证明是一个强大的估计的共振散射贡献弗里德尔对立，很少受到影响的结构，也不是由占领的特殊位置的特定空间群。在介绍非手性非中心对称晶体结构的文章中有相当多的混乱。建议提供了最佳的方式来处理非中心对称的晶体结构的实验者没有兴趣在确定的绝对结构。
All the 139 noncentrosymmetric crystal structures published in Acta Crystallographica Section C between January 2011 and November 2012 inclusive have been used as the basis of a detailed study of the reporting of absolute structure. These structure determinations cover a wide range of space groups, chemical composition and resonant-scattering contribution. Defining A and D as the average and difference of the intensities of Friedel opposites, their level of fit has been examined using 2AD and selected-D plots. It was found, regardless of the expected resonant-scattering contribution to Friedel opposites, that the Friedel-difference intensities are often dominated by random uncertainty and systematic error. An analysis of data collection strategy is provided. It is found that crystal-structure determinations resulting in a Flack parameter close to 0.5 may not necessarily be from crystals twinned by inversion. Friedifstat is shown to be a robust estimator of the resonant-scattering contribution to Friedel opposites, very little affected by the particular space group of a structure nor by the occupation of special positions. There is considerable confusion in the text of papers presenting achiral noncentrosymmetric crystal structures. Recommendations are provided for the optimal way of treating noncentrosymmetric crystal structures for which the experimenter has no interest in determining the absolute structure.
DOI：
10.1107/s010876731004287x
发表时间：
2011-01-01
期刊：
ACTA CRYSTALLOGRAPHICA SECTION A
影响因子：
--
作者：
Flack, H. D.;Sadki, M.;Watkin, D. J.
通讯作者：
Watkin, D. J.