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

© International Union of Crystallography 2006
International Tables for Crystallography (2006). Vol. C. ch. 8.7, p. 728

Section 8.7.4.4.5. Polarized neutron scattering in the noncentro­symmetric case

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

8.7.4.4.5. Polarized neutron scattering in the noncentro­symmetric case

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If the space group is noncentrosymmetric, both [F_N] and M have a phase, [\varphi_N] and [\varphi_M], respectively.

If for simplicity one assumes α = π/2, and, defining δ = φM − φN, [R = {1+|x|^2 + 2|x| \cos\delta \over 1+ |x|^2 - 2|x| \cos\delta}, \eqno (8.7.4.46)]which shows that |x| and δ cannot both be obtained from the experiment.

The noncentrosymmetric case can only be solved by a careful modelling of the magnetic structure factor as described in Subsection 8.7.4.5[link].

In practice, neither the polarization of the incident beam nor the efficiency of the r.f. flipping coil is perfect. This leads to a modification in the expression for the flipping ratios [see Section 6.1.3[link] or Forsyth (1980[link])].

References

First citation Forsyth, J. B. (1980). In Electron and magnetization densities in molecules and solids, edited by P. Becker. New York/London: Plenum.Google Scholar








































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