Can a multipole analysis faithfully reproduce topological descriptors of a total charge density?

• Published in: Acta crystallographica. Section A, Foundations of crystallography Foundations of crystallography, 2002-09, Vol.58 (5), p.451-459
• Main Authors: Bytheway, Ian, Chandler, Graham S., Figgis, Brian N.
• Format: Article
• Language: English
• Subjects: atoms in molecules; charge density; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; multipole analysis; Physics; Single-crystal and powder diffraction; Structure of solids and liquids; crystallography; X-ray diffraction and scattering
• ISSN: 0108-7673; 1600-5724
• DOI: 10.1107/S0108767302008759

Total charge densities ρ(r) of solid NH3 have been derived using an ab initio crystalline molecular‐orbital approach and also from multipole refinement of the structure factors obtained from the same charge density. Comparison of the topological features of these charge densities, as defined by the quantum theory of atoms in molecules, has been used to probe the ability of the multipole analysis to reproduce exactly known total charge‐density distributions. For the most part, multipole refinement satisfactorily returns the features of the original density, although the fit to theoretical data is not as good as that to the experimental data. The one topological parameter that is poorly reproduced is the Laplacian at NH bond critical points.