SEGREGATIONS IN DISORDERED CLOSE-PACKED STRUCTURES AND RELATED DIFFUSE-SCATTERING IN COBALT AND COBALT ALLOYS .1. MODEL INTENSITY CALCULATIONS AND GENERAL EFFECTS

Diffraction from well-ordered polytypic 2H, 3C, 4H, 9R, 5T and one-dim ensionally disordered close-packed structures containing segregations of dilute atoms or impurities is considered. The diffuse scattering wa s calculated by the Monte Carlo technique. Anomalous diffuse scatterin g contributions were found along the H-K=0 (mod 3) reciprocal-lattice rows of perfect (without stacking disorder) crystals as well as in one -dimensionally disordered crystals with a correlated distribution of s egregations. Details of the intensity redistribution, and the shift an d asymmetry of diffuse reflections are reported.