The influence of preferred orientation on the line width and peak shift of (hk) interferences

The evaluation of interference effects produced by two-dimensional lattices is a problem which arises in studies of disordered lamellar structure, e.g. non-graphitic C atoms. For isotropic polycrystalline samples the shapes of the interference lines depend only on the crystallite size and the lattice imperfections. In anisotropic samples the line shapes also vary, however, with the degree of preferred orientation. Using a theoretical treatment already developed [Ruland & Tompa Acta Cryst. (1968) A24, 93] the variations of the half-width and the peak shift of these lines have been computed as functions of a complete range of preferred orientation for a system of cylindrical symmetry. The results permit the assessment of the magnitude of the effect of preferred orientation on these lines for various degrees of preferred orientation and for various directions of measurement with respect to the principal axis and thus enable one to make appropriate corrections in the determination of apparent layer sizes. The significance of a variation of apparent layer sizes with the direction of measurement is discussed.