Towards Automatic Indexing of the Laue Diffraction Pattern

Abstract

A method is presented for the semi‐automatic indexing of the Laue diffraction pattern. The method is based on the recognition of conics in the Laue pattern by a plane‐search algorithm in reciprocal space, after which possible cells are constructed in direct space and relative cell parameters and crystal orientation are obtained. These cells, scaled to an arbitrary volume, are refined, reduced and grouped in order of frequency of occurrence. Usually, the cell that occurs most frequently is the correct one. Other cells found have one or more axes doubled. Such cells are easily discriminated by comparison of the corresponding simulated Laue pattern with the measured one. The method is tested with different data sets of an organic and an organometallic compound collected with an image plate using white radiation of a molybdenum sealed tube. For each pattern, the correct cell was found. Further refinement of the relative cell parameters by matching of the calculated and observed positions of the Lane spots showed good agreement with the relative cell parameters obtained from monochromatic data. To scale the cells, additional information is needed. This paper demonstrates the use of the Mo emission line Kβ1 to determine the cell volume within 1.2%.

Automated indexing for texture and strain measurement with broad-bandpass x-ray microbeams

“…The indexing approach outlined in this article is quite distinct from methods which have been described previously, [10][11][12] and has the advantages that it requires only a few reflections (Ͼ4 per grain͒, and can process overlapping Laue patterns generated by multiple grains.…”

XMAS: A Versatile Tool for Analyzing Synchrotron X-ray Microdiffraction Data

“…The main drawback of the most popular software packages such as OrientExpress (Laugier and Bochu, 1999) and LaueX (Soyer, 1996) is that they require a fair amount of user intervention as they are mainly aimed to index isolated patterns of single crystals to determine their orientation. Specific software for indexing macromolecular and protein crystal patterns for Laue structure refinement have also been developed, including Lauegen (Campbell, 1995), Laueview (Srajer et al, 2000) and Lauecell (Ravelli et al, 1996). These software suites, written for macromolecular Laue crystallography, are not, however, well suited for indexing small lattice parameter cells, which often require the use of reflective geometry with the detector at an angle, instead of the more conventional transmission geometry.…”

X-ray Laue Diffraction Microscopy in 3D at the Advanced Photon Source

“…If the energy (wavelength) of the Laue reflections is unknown, only deviatoric strain (unit cell shape) can be determined because a unit cell with the same shape and orientation but different volume will produce the same Laue pattern reflecting different energies. The full strain tensor can be further obtained by measuring the energy of one or more reflections with a monochromatic beam or by measuring the energy of one or more Laue reflections (Sheremetyev et al, 1991;Ravelli et al, 1996;Park et al, 1997;Wenk et al, 1997;Chung and Ice, 1999;Tamura et al, 2003). With a micro-focused beam, precise measurements of local crystallographic orientations (micro-texture) and local strain distributions become feasible, and thus the X-ray Laue diffraction microscopy provides a powerful tool for materials science studies.…”