Extinction correction in white X-ray and neutron diffraction

Abstract

Extinction effects in white-beam X-ray and neutron diffraction are considered following the formulation developed for monochromatic-beam diffraction by Becker & Coppens [Acta Cryst. (1974), A30,129-147]. In white-beam diffraction, a small deviation of the wavelength from the Bragg condition A2 is a variable which represents the line profile of the diffraction peaks, so that by using the new parameter A2 the theory is converted to one in white-beam diffraction. It is shown that for a convex crystal, primary extinction yp agrees with the results calculated already for monochromatic diffraction. The same relation is shown to hold in secondary extinction y,. It is concluded that extinction theory derived for monochromatic diffraction is applicable without any modification in whitebeam diffraction.

Wavelength-dependent measurements of extinction in an extended-face crystal of zinc selenide

“…[One of the main consequences of the additional sin 20 factor is that the differentiation between type I and type II crystals becomes less distinct for severe extinction.] It is worth noting that Tomiyoshi, Yamada & Watanabe (1980) have shown that extinction correction in white-beam diffraction agrees with that in monochromatic-beam diffraction. The selection of several pairs of observations enables one to test the consistency of the derived values of extinction parameters and the ability of the extinction theory to account for the wavelength dependence.…”

Accuracy of single-crystal time-of-flight neutron diffraction: a comparative study of MnF2

“…Application of the Becker & Coppens mixed-type model (refinement of both the particle size and mosaic spread including primary extinction) produced unphysical results. Though the above models were derived originally for monochromatic diffraction, they remain valid when applied to white-beam diffraction (Tomiyoshi, Yamada & Watanabe, 1980).…”

Extinction in the framework of transfer equations for general-type crystals

“…In this method the incident beam is well collimated, but it has uniform wavelength distribution of intensity. In the following the angular dispersive method and the energy dispersive method will be treated together, as they are characterized by the same extinction factor (Tomiyoshi, Yamada & Watanabe, 1980). The Bragg cross depend on k~ and difference -more section for a given block does not k 2 separately; it depends on their exactly, on the vector h= k2-k I -H, block.…”