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Concerning an unnecessary approximation made by Zachariasen in treating the perfect-crystal Bragg case

1978; International Union of Crystallography; Volume: 34; Issue: 2 Linguagem: Inglês

10.1107/s0567739478000625

1600-8596

S. Wilkins,

Geophysics and Sensor Technology

An approximation in Zachariasen's [Theory of X-Ray Diffraction in Crystals (1945). New York: John Wiley] treatment of X-ray diffraction from a perfect plane-parallel crystal in the Bragg case is pointed out and eliminated. The corresponding unapproximated expression for the transmitted beam is also given. It transpires that Zachariasen's approximation leads to significant errors for 'thin' crystals (i.e. those for which the path length is less than or of the order of the extinction length). Some illustrations of the nature of the error are given.