The uncorrelated block model

Sabine, T. M.

doi:10.1107/97809553602060000603

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

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International Tables for Crystallography (2006). Vol. C. ch. 6.4, p. 611

Section 6.4.10.2. The uncorrelated block model

T. M. Sabine^a

^a ANSTO, Private Mail Bag 1, Menai, NSW 2234, Australia

6.4.10.2. The uncorrelated block model

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When this model is used, two values of x are required. These are designated [x_p] for primary extinction and [x_s] for secondary extinction. Equation (6.4.8.1) is used to obtain a value for [x_p] . The primary-extinction factors are then calculated from (6.4.5.3), (6.4.5.4) and (6.4.5.5), and $[E_p(2\theta)]$ is given by equation (6.4.7.1). In the second step, [x_s] is obtained from equation (6.4.9.1), and the secondary-extinction factors are calculated from either (6.4.9.2) and (6.4.9.3) or (6.4.9.4) and (6.4.9.5). The result of these calculations is then used in equation (6.4.7.1) to give $[E_s(2\theta)]$ . It is emphasised that [x_s] includes the primary-extinction factor. Finally, $[E(2\theta)=E_p(2\theta) E_s[E_p(2\theta),2\theta] ]$ .

Application of both models to the analysis of neutron diffraction data has been carried out by Kampermann, Sabine, Craven & McMullan (1995).

References

Kampermann, S. P., Sabine, T. M., Craven, B. M. & McMullan, R. K. (1995). Hexamethylenetetramine: extinction and thermal vibrations from neutron diffraction at six temperatures. Acta Cryst. A51, 489–497.Google Scholar

International Tables for Crystallography (2006). Vol. C. ch. 6.4, p. 611