Tables for
Volume C
Mathematical, physical and chemical tables
Edited by E. Prince

International Tables for Crystallography (2006). Vol. C, ch. 8.7, p. 714


P. Coppens,a Z. Sub and P. J. Beckerc

a732 NSM Building, Department of Chemistry, State University of New York at Buffalo, Buffalo, NY 14260-3000, USA,bDigital Equipment Co., 129 Parker Street, PKO1/C22, Maynard, MA 01754-2122, USA, and cEcole Centrale Paris, Centre de Recherche, Grand Voie des Vignes, F-92295 Châtenay Malabry CEDEX, France

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Definition of difference density functions

[\Delta \rho = {2 \over V} \left\{\sum\limits_0^{1/2} (A_1 - A_2)\cos2\pi{\bf h} \cdot {\bf r} + \sum\limits_0^{1/2} (B_1 -B_2)\sin 2\pi {\bf h} \cdot {\bf r} \right\}] with F = A + iB.

(a) Residual map A1, B1 from observations calculated with model phases.
A2, B2 from refinement model.
(b) X − X deformation map A1, B1 from observation, with model phases.
A2, B2 from high-order refinement, free-atom model, or other reference state.
(c) X − N deformation map [as (b) but] A2, B2 calculated with neutron parameters.
(d) X − (X + N) deformation map [as (b) but] A2, B2 calculated with parameters from joint refinement of X-ray neutron data.
(e) X − X, X − N, X − (X + N) valence map As (b), (c), (d) with A1, B1 calculated with core-electron contribution only.
(f) Dynamic model map A1, B1 from model.
A2, B2 with parameters from model refinement and free-atom functions.
(g) Static model map ρmodel − ρfree atom, where ρmodel is sum of static model density functions.