Simulation of X-ray traverse topographs and synchrotron Laue topographs: application of the reciprocity theorem

A new demonstration of the reciprocity theorem of optics in the case of the X-ray dynamical theory is given. It is applied to the simulation of traverse and white-beam synchrotron topographs. It is shown that the accuracy of a new numerical algorithm [Carvalho & Epelboin (1993). Acta Cryst. A49, 460-467] allows the use of the reciprocity theorem. Its main advantage is to decrease the time of computation by at least an order of magnitude and to permit a strategy to be built for the quantitative study of defects, starting with simulations of poor resolution and increasing resolution only in worthwhile areas. This was not possible with the previous method.