On the calculation of small-angle diffraction patterns from distorted lattices

A method is presented for the calculation of the diffraction properties of distorted lattices. An isotropic correlation field is used and the influence of finite crystal size is taken into account. An approximate model is described which is based on a fit of the correlation function to a sum of Gaussians. This method, which is applicable to more complex structures than simple lattices, simplifies the calculation of complicated convolution integrals. The method is illustrated with the calculation of the diffraction properties of 2D hexagonal lattices and exponential correlation. Various aspects, such as variations in peak intensity, line width and line shifts, are discussed. (orig.)