On the Relationship between Thermal Vibrations and X-Ray Diffuse Scatterings by Polymer Crystals. II. X-Ray Diffuse Scattering by Polymer Crystals

A theory of X-ray diffraction from polymer crystals accompanying with thermal disorders is developed under harmonic approximation. Temperature factor based on the displacement in the radial direction (in cylindrical coordinates) is given in terms of modified Bessel functions. A new selection rule which depends on thermal vibrational mode is derived, so that it is shown that the strong diffuse streak scattering appears on N 0 -th layer line ( N 0 is the number of turns of the helix in its repeat unit), when interaction energies between polymer chains are weak enough.