title: Multigrain indexing of unknown multiphase materials.
abstract: A multigrain indexing algorithm for use with samples comprising an arbitrary number of known or unknown phases is presented. Noa prioricrystallographic knowledge is required. The algorithm applies to data acquired with a monochromatic beam and a conventional two-dimensional detector for diffraction. Initially, candidate grains are found by searching for crystallographic planes, using a Dirac comb convoluted with a box function as a filter. Next, candidate grains are validated and the unit cell is optimized. The algorithm is validated by simulations. Simulations of 500 cementite grains and ∼100 reflections per grain resulted in 99.2% of all grains being indexed correctly and 99.5% of the reflections becoming associated with the right grain. Simulations with 200 grains associated with four mineral phases and 50-700 reflections per grain resulted in 99.9% of all grains being indexed correctly and 99.9% of the reflections becoming associated with the right grain. The main limitation is in terms of overlap of diffraction spots and computing time. Potential areas of use include three-dimensional grain mapping, structural solution and refinement studies of complex samples, and studies of dilute phases.
authors.affiliation: Department of Physics, Technical University of Denmark , Building 307, Fysikvej, Kongens Lyngby, 2800, Denmark.
authors.forename: Christian
authors.initials: C
authors.lastname: Wejdemann
authors.affiliation: Department of Physics, Technical University of Denmark , Building 307, Fysikvej, Kongens Lyngby, 2800, Denmark.
authors.forename: Henning Friis
authors.initials: HF
authors.lastname: Poulsen
keywords: 3DXRD; indexing; multigrain crystallography; three-dimensional X-ray diffraction microscopy