ESTIMATION OF THE MOSAIC SPREAD AND THE MOSAIC-BLOCK SIZE OF ZINC SINGLE-CRYSTAL SPHERES BY SIMULATIONS OF PSI-SCANS WITH UMWEG90

In a previous paper [Rossmanith (1992). Acta Cryst. A48, 596-610], new formulae for the Lorentz factor and peak width for single and multipl e diffraction were given. These formulae are used in the program UMWEG 90 for the calculation of psi-scan simulations. In this paper, simulat ions are compared with five different psi scans of two different zinc single-crystal spheres measured with Mo and Ag Kalpha radiations, resp ectively. It is shown that, by fitting the calculated to the measured psi scans, consistent and physically significant parameters for the mo saic structure parameters - mosaic spread and mosaic-block size - and for the divergence parameters of the X-ray beam are obtained. Moreover , it is shown that the parameters obtained from multiple-diffraction e xperiments are consistent with those resulting from single-diffraction experiments performed with synchrotron radiation.