Crystal Structures Elucidated from X-ray Powder Diffraction Data without Prior Indexing

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• 作者：Clifford W. Padgett ; Hadi D. Arman ; William T. Pennington
• 刊名：Crystal Growth & Design
• 出版年：2007
• 出版时间：February 2007
• 年：2007
• 卷：7
• 期：2
• 页码：367 - 372
• 全文大小：207K
• 年卷期：v.7,no.2(February 2007)
• ISSN：1528-7505

文摘

OCEANA, a new genetic algorithm-based program for structure elucidation from non-indexed X-ray powder diffractiondata, uses Lamarckian evolution to search for the best molecular position and orientation over a range of cell parameters for a givenspace group. As OCEANA does not require an indexed powder pattern, it is particularly suited for analysis of organic molecularcrystals, which often crystallize in relatively large, low-symmetry unit cells. The high degree of peak overlap in the powder patternsof such compounds makes cell determination and pattern indexing very difficult and presents a major obstacle to success whenusing any routine that requires this information. OCEANA searches within a user-defined range of cell parameters for a specifiedspace group and uses the experimental density to eliminate unit cells that are not viable. Several examples based on compoundswith known crystal structures are presented to demonstrate the effectiveness of this method, and the crystal structure of a newcompound, bis(5-quinoline)diacetylene (5QDA), is also reported.