Computer simulation of diffuse X-ray scattering by an aligned smectic C-like nematic phase

We report a new method for the quantitative analysis of diffuse X-ray scattering by some disordered smectic phases. Computer simulations of diffuse X-ray scattering are compared with actual diffraction patterns of a series of oriented liquid crystalline polymers TDI-CmCn. The simulation shows that both Bragg peaks (spots) and equidistant streaks (diffuse scatterings) are diffracted by one smectic C-like structure in which each of the molecular chains is displaced from its mean position by a random distance Delta (z), along the chain axis (z). This is a first type of disorder. By assuming a Gaussian distribution of the disordered displacements, the mean value of Delta (z) has been determined from the position and intensity of the streaks and Bragg peaks for the polymers.