A global optimization approach to automated indexing of fiber diffraction patterns

Accurate determination of cell parameters from two-dimensional wide-angle X-ray diffraction patterns of oriented polymer crystals is critical for structural analysis. This process, known as indexing, can be challenging due to the complexity of the diffraction patterns. Here, we introduce a method that synergistically combines genetic algorithms with gradient-based optimization techniques to progressively refine diffraction pattern matching. This approach is implemented in an automated computational tool named PolymCrystIndex. The method's versatility allows it to be applied to various crystal systems, including orthorhombic, monoclinic and triclinic, as demonstrated by its successful testing on experimental data from different polymers. PolymCrystIndex will provide a fast and reliable solution for indexing fiber patterns and obtaining accurate cell parameters, advancing the field of polymer crystallography.