Analysing Friedel averages and differences.

IF 1.8 4区材料科学

Acta Crystallographica Section A Pub Date : 2012-11-01 Epub Date: 2012-10-18 DOI:10.1107/S0108767312034885

Simon Parsons, Phillip Pattison, Howard D Flack

引用次数: 28

Abstract

Various practical applications of the average (A) and difference (D) of Friedel opposites are described. Techniques based on the resonant-scattering contribution to Friedel differences are applied to see whether a crystal is centrosymmetric or not, and to determine the point group of the crystal. For the validation of a structural study, plots of A(obs) against A(model), and D(obs) against D(model) are used extensively. Moreover, it is useful to display both plots on the same graph. Intensity measurements on a crystal of NaClO(3) were made at three different speeds, with two different radiations and two different diffractometers, and treated with two different software packages and four different absorption corrections. The evaluation of these numerous data sets reveals underlying deficiencies. For comparison, plots of A(obs) against A(model), and D(obs) against D(model) are presented for two centrosymmetric crystals.

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分析弗里德尔平均和差异。

描述了弗里德尔对差的平均(A)和差(D)的各种实际应用。基于共振散射对弗里德尔差异贡献的技术被应用于观察晶体是否中心对称，并确定晶体的点群。为了验证结构研究，广泛使用了a (obs)对a(模型)和D(obs)对D(模型)的图。此外，在同一图上显示两个图是有用的。在三种不同的速度下，用两种不同的辐射和两种不同的衍射仪对NaClO(3)晶体进行了强度测量，并用两种不同的软件包和四种不同的吸收校正进行了处理。对这些大量数据集的评估揭示了潜在的缺陷。为了比较，给出了两个中心对称晶体A(obs)对A(模型)和D(obs)对D(模型)的对比图。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Acta Crystallographica Section A 化学-晶体学

自引率

11.10%

发文量

审稿时长

3 months

期刊介绍： Acta Crystallographica Section A: Foundations and Advances publishes articles reporting advances in the theory and practice of all areas of crystallography in the broadest sense. As well as traditional crystallography, this includes nanocrystals, metacrystals, amorphous materials, quasicrystals, synchrotron and XFEL studies, coherent scattering, diffraction imaging, time-resolved studies and the structure of strain and defects in materials. The journal has two parts, a rapid-publication Advances section and the traditional Foundations section. Articles for the Advances section are of particularly high value and impact. They receive expedited treatment and may be highlighted by an accompanying scientific commentary article and a press release. Further details are given in the November 2013 Editorial. The central themes of the journal are, on the one hand, experimental and theoretical studies of the properties and arrangements of atoms, ions and molecules in condensed matter, periodic, quasiperiodic or amorphous, ideal or real, and, on the other, the theoretical and experimental aspects of the various methods to determine these properties and arrangements.