FELIX: an algorithm for indexing multiple crystallites in X-ray free-electron laser snapshot diffraction images

Kenneth R. Beyerlein, Thomas A. White, Oleksandr Yefanov, Cornelius Gati, Ivan G Kazantsev, Nicolai Fog Gade-Nielsen, Peter Mahler Larsen, Henry N. Chapman, Søren Schmidt

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A novel algorithm for indexing multiple crystals in snapshot X-ray diffraction images, especially suited for serial crystallography data, is presented. The algorithm, FELIX, utilizes a generalized parametrization of the Rodrigues-Frank space, in which all crystal systems can be represented without singularities. The new algorithm is shown to be capable of indexing more than ten crystals per image in simulations of cubic, tetragonal and monoclinic crystal diffraction patterns. It is also used to index an experimental serial crystallography dataset from lysozyme microcrystals. The increased number of indexed crystals is shown to result in a better signal-to-noise ratio, and fewer images are needed to achieve the same data quality as when indexing one crystal per image. The relative orientations between the multiple crystals indexed in an image show a slight tendency of the lysozme microcrystals to adhere on (110) facets.
Original languageEnglish
JournalJournal of Applied Crystallography
Issue number4
Pages (from-to)1075-1083
Number of pages9
Publication statusPublished - 2017


  • Serial crystallography
  • SFX
  • Materials science
  • Structural biology

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