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

International Tables for Crystallography (2006). Vol. C. ch. 8.7, p. 732

Section 8.7.4.9. Combined charge- and spin-density analysis

P. Coppens,a Z. Sub and P. J. Beckerc

a 732 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

8.7.4.9. Combined charge- and spin-density analysis

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Combined charge- and spin-density analysis requires performing X-ray and neutron diffraction experiments at the same temperature. Magnetic neutron experiments are often only feasible around 4 K, and such conditions are more difficult to achieve by X-ray diffraction. Even if the two experiments are to be performed at different temperatures, it is often difficult to identify compounds suitable for both experiments.

Owing to the common parametrization of ρ(r) and s(r), a combined least-squares-refinement procedure can be implemented, leading to a description of [\rho_\uparrow({\bf r})] and [\rho_\downarrow({\bf r})], the spin-dependent electron densities. Covalency parameters are obtainable together with spin polarization effects in the closed shells, by allowing [\rho_\uparrow] and [\rho_\downarrow] to have different radial behaviour.

Spin-polarization effects would be difficult to model from the spin density alone. But the arbitrariness of the modelling is strongly reduced if both ρ and s are analysed at the same time (Becker & Coppens, 1985[link]; Coppens, Koritsanszky & Becker, 1986[link]).

References

First citation Becker, P. & Coppens, P. (1985). About the simultaneous interpretation of charge and spin density data. Acta Cryst. A41, 177–182.Google Scholar
First citation Coppens, P., Koritsanszky, T. & Becker, P. (1986). Transition metal complexes: what can we learn by combining experimental spin and charge densities? Chem. Scr. 26, 463–467.Google Scholar








































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