title: X-ray structure refinement using aspherical atomic density functions obtained from quantum-mechanical calculations.
abstract: An approach is outlined for X-ray structure refinement using atomic density fragments obtained by Hirshfeld partitioning of quantum-mechanical density fragments. Results are presented for crystal structure refinements of urea and benzene using these 'Hirshfeld atoms'. Using this procedure, the quantum-mechanical non-spherical electron density is taken into account in the structural model based on the conformation found in the crystal. Contrary to current consensus in structure refinement, the anisotropic displacement parameters of H atoms can be reproduced from neutron diffraction measurements simply from a least-squares fit using the Hirshfeld atoms derived from the BLYP level of theory and including a simple point-charge model to treat the crystal environment.
authors.affiliation: Chemistry, School of Biomedical and Chemical Sciences, The University of Western Australia, Crawley 6009, Australia.
authors.forename: Dylan
authors.initials: D
authors.lastname: Jayatilaka
authors.forename: Birger
authors.initials: B
authors.lastname: Dittrich
mesh_terms: D016880:Anisotropy; D001554:Benzene / Q000737:chemistry; D018360:Crystallography, X-Ray / Q000379:methods*; D008956:Models, Chemical; D011789:Quantum Theory; D014508:Urea / Q000737:chemistry
chemical_list: D014508:Urea; D001554:Benzene