SIMULATION OF X-RAY-DIFFRACTION FOR SUPERLATTICES WITH FLUCTUATIONS FROM PERFECT PERIODICITY

An investigation on the effects of the disorder of superlattice periods on x-ray-diffraction patterns is reported. Three kinds of disorder (random fluctuations, systematic deviations, and local deviations) have been considered. The results of the simulations show that their effects are quite different. The systematic deviation widens the superlattice peaks and shifts the positions of the low-angle superlattice peaks. The effect of the systematic deviation on the reduction of peak intensity is more serious than that of random fluctuation. The local deviation makes the superlattice peak weaker and wider or splits it into double peaks. These three kinds of disorder can be distinguished.