ISSN:
1600-5724
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
For short wavelengths, Umweganregung cannot be experimentally eliminated. Its average unscaled intensity for a random orientation of the crystal is U(2θ1) = ∫θ, φ (sin 2 θ/sin 2θ1)P(θ1, θ, φ) exp [-2K(sin2 θ + sin2 θ12)] dθ dφ, where (2θ, φ) are the spherical coordinates of a point on the Ewald sphere when the intensity measurement is made at (2θ1, 0), the angle between the two directions being 2θ12, while K is the slope of a plot of In (F(obs)) as a function of sin2 θ, and P(θ1, θ, φ) is the polarization correction appropriate to the double reflection. Diffraction intensities were measured for epidote and quartz. A plot of (|F(calc)|)/(F(obs)) as a function of F(obs) for epidote was considerably improved by the subtraction from each intensity measurement of a number of counts SU(2θ1), where S is an experimental scale factor while U(2θ1) was calculated for epidote by numerical integration over the Ewald sphere. The refinement residuals for both compounds improved after correction of the intensities and the weights.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0567739479000139
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