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  • Title: Multipole electron densities and atomic displacement parameters in urea from accurate powder X-ray diffraction.
    Author: Svane B, Tolborg K, Jørgensen LR, Roelsgaard M, Jørgensen MRV, Brummerstedt Iversen B.
    Journal: Acta Crystallogr A Found Adv; 2019 Jul 01; 75(Pt 4):600-609. PubMed ID: 31264644.
    Abstract:
    Electron density determination based on structure factors obtained through powder X-ray diffraction has so far been limited to high-symmetry inorganic solids. This limit is challenged by determining high-quality structure factors for crystalline urea using a bespoke vacuum diffractometer with imaging plates. This allows the collection of data of sufficient quality to model the electron density of a molecular system using the multipole method. The structure factors, refined parameters as well as chemical bonding features are compared with results from the high-quality synchrotron single-crystal study by Birkedal et al. [Acta Cryst. (2004), A60, 371-381] demonstrating that powder X-ray diffraction potentially provides a viable alternative for electron density determination in simple molecular crystals where high-quality single crystals are not available.
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