![]() ![]() In this way, one can determine the crystallographic orientations of arbitrarily oriented crystals (Warren, 2016 Larson et al., 2002 ). The pattern of reflections arising on a detector is then a direct fingerprint of the orientation of the crystal lattice, assuming one knows the structure of the unit cell of the crystal (Moffat et al., 1984 Smallman & Ngan, 2014 ). Other strategies for collecting multi-reflection BCDI data include obtaining important information about the crystallographic orientation of an isolated specimen before a BCDI experiment from other techniques, either scanning extensive volumes of reciprocal space until a reflection is found or by performing Laue diffraction beforehand at a different instrument (Newton et al., 2009 Hofmann et al., 2017, 2020 ).Ī broadband (pink) X-ray beam permits Laue diffraction patterns to be measured from a lattice. For well faceted nanocrystals and when either the Miller indices of a measured reflection or the growth direction of the crystals is known in advance, it is shown that the orientation can be inferred by spinning the crystal until multiple reflections light up and indexing the pole figure using texture analysis algorithms (Richard et al., 2018 ). As a result, it is often extremely difficult to measure more than one Bragg peak, thus it is impossible to obtain all the components of the strain tensor (Newton et al., 2009 ). BCDI is compatible with operando measurements under different external stimuli, such as compression or tension, femtosecond laser light pulses, electric and magnetic fields allowing the visualization of evolving strain inside nanoparticles and ultimately the investigation of materials properties at the nanoscale (Clark et al., 2013, 2014, 2015 Ulvestad et al., 2015, 2017 Pateras et al., 2019 Cherukara et al., 2017 Björling et al., 2019 Takahashi et al., 2013 Newton et al., 2019 ).Ī frequent challenge faced in BCDI experiments is that it relies on satisfying the Bragg condition of a single-crystalline grain within a potentially large population of sub-micrometre scale crystals or grains with unknown crystallographic orientations. Bragg coherent X-ray diffraction imaging (BCDI) allows the visualization of the local atomic lattice displacement of single nanoparticles or grains in three dimensions. Particularly in micrometre- to nanometre-scale dimensions, the knowledge of the crystallographic orientation and full strain tensor are important pieces of information for predicting the mechanical properties of submicrometre particles and crystal grains of polycrystalline materials (Cherukara et al., 2018 a ). Elastic constants are typically defined with respect to bulk while their values deviate and need to be measured explicitly in the case of two-dimensional materials or nanometre-sized objects (El-Atwani et al., 2019 Gigax et al., 2019 ). Crystal slip has been shown to enhance surface diffusional creep and lead to unusual superplastic behavior of silver nanocrystals (Zhong et al., 2017 ). Dislocation locking, for example, is considered an effective physical mechanism to boost the hardness of polycrystalline metals (Spiecker et al., 2019 ). Macroscopic properties of crystalline materials depend on their atomic structure, dimensionality and other nanoscale phenomena. The design, concept of operation, the developed procedures for indexing Laue patterns, and automated measuring of Bragg coherent diffraction data from multiple reflections of the same nanocrystal are discussed. With a proper orientation matrix determined for the lattice, one can measure coherent diffraction patterns near multiple Bragg peaks, thus providing sufficient information to image the full strain tensor in 3D. The new instrument enables, through rapid switching from monochromatic to broadband (pink) beam, the use of Laue diffraction to determine crystal orientation. Here, the commissioning of a movable double-bounce Si (111) monochromator at the 34-ID-C endstation of the Advanced Photon Source is reported, which aims at delivering multi-reflection BCDI as a standard tool in a single beamline instrument. However, even when the signal from a single Bragg reflection with ( hkl) Miller indices is found, the crystallographic axes on the retrieved three-dimensional (3D) image of the crystal remain unknown, and thus localizing in reciprocal space other Bragg reflections becomes time-consuming or requires good knowledge of the orientation of the crystal. Measurement modalities in Bragg coherent diffraction imaging (BCDI) rely on finding a signal from a single nanoscale crystal object which satisfies the Bragg condition among a large number of arbitrarily oriented nanocrystals. ![]()
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