UMWEG: a program for the calculation and graphical representation of multiple-diffraction patterns. I. Polarization

The expressions concerning the polarization in the three-beam case used in the program UMWEG [Rossmanith (2003). J. Appl. Cryst. 36, 1467–1474] are given. As an application, the effect of polarization on the intensities of multiple-diffraction patterns, as well as on the asymmetries of three-beam interference profiles, is discussed. Examples for the inversion of the asymmetry of three-wave intensity profiles for π-polarized incident radiation [Juretschke (1986). Phys. Status Solidi B, 135, 455–466] are presented.