International
Tables for Crystallography Volume B Reciprocal space Edited by U. Shmueli © International Union of Crystallography 2006 |
International Tables for Crystallography (2006). Vol. B, ch. 5.1, p. 545
Section 5.1.6.6. Thin crystals – comparison with geometrical theory^{a}Laboratoire de Minéralogie-Cristallographie, Université P. et M. Curie, 4 Place Jussieu, F-75252 Paris CEDEX 05, France |
Using (5.1.6.6) and (5.1.6.7), the reflecting power of the reflected beam may also be written where and When is very small, tends asymptotically towards the function and towards the value given by geometrical theory. The condition for geometrical theory to apply is, therefore, that the crystal thickness be much smaller than the Pendellösung distance. In practice, the two theories agree to within a few per cent for a crystal thickness smaller than or equal to a third of the Pendellösung distance [see Authier & Malgrange (1998)].
References
Authier, A. & Malgrange, C. (1998). Diffraction physics. Acta Cryst. A54, 806–819.