FWR: a computer program for refining the molecular structure in the crystalline phase of polymers based on the analysis of the whole X-ray fiber diffraction patterns

The program FWR (fiber whole diffraction pattern refinement) for structure refinement of polymers is presented. The constrained least-squares procedure is employed in order to fit the whole two-dimensional diffraction pattern from a fiber sample of a polymer. Both structural and morphological parameters can be refined, thus providing a wide characterization of the material. Refinable parameters are: bond lengths, valence and torsion angles, averaged crystallite size, cell parameters, orientation degree of crystallites, tilt angle (if any) of crystallites with respect to the fiber axis and thermal and strain parameters (distortion of the second kind).