Habermehl Stefan, Mörschel Philipp, Eisenbrandt Pierre, Hammer Sonja M, Schmidt Martin U
Institute of Inorganic and Analytical Chemistry, Goethe University, Max-von-Laue-Str. 7, D-60438 Frankfurt am Main, Germany.
Acta Crystallogr B Struct Sci Cryst Eng Mater. 2014 Apr;70(Pt 2):347-59. doi: 10.1107/S2052520613033994. Epub 2014 Mar 28.
A method to refine organic crystal structures from powder diffraction data with incorrect lattice parameters has been developed. The method is based on the similarity measure developed by de Gelder et al. [J. Comput. Chem. (2001), 22, 273-289], using the cross- and auto-correlation functions of a simulated and an experimental powder pattern. The lattice parameters, molecular position, molecular orientation and selected intramolecular degrees of freedom are optimized until the similarity measure reaches a maximum; subsequently, a Rietveld refinement is carried out. The program FIDEL (FIt with DEviating Lattice parameters) implements this method. The procedure is also suitable for unindexed powder data, powder diagrams of very low quality and powder diagrams of non-phase-pure samples. Various applications are shown, including structure determinations from powder data using crystal structure predictions by standard force-field methods. Other useful applications include the automatic structure determination from powder data starting from the crystal structures of isostructural compounds (e.g. a solvate, hydrate or chemical derivative), or from crystal data measured at a different temperature or pressure.
已开发出一种从具有错误晶格参数的粉末衍射数据中精修有机晶体结构的方法。该方法基于de Gelder等人[《计算化学杂志》(2001年)，22卷，273 - 289页]开发的相似性度量，使用模拟粉末图案和实验粉末图案的互相关函数和自相关函数。优化晶格参数、分子位置、分子取向和选定的分子内自由度，直到相似性度量达到最大值；随后，进行Rietveld精修。程序FIDEL(具有偏差晶格参数的拟合)实现了该方法。该程序也适用于未索引的粉末数据、质量非常低的粉末图谱和非纯相样品的粉末图谱。展示了各种应用，包括使用标准力场方法通过晶体结构预测从粉末数据确定结构。其他有用的应用包括从同构化合物(如溶剂化物、水合物或化学衍生物)的晶体结构开始，或从在不同温度或压力下测量的晶体数据，从粉末数据自动确定结构。
