![]() ![]() Several approaches of electron diffraction in TEM for the unit-cell determination of a crystal have been developed. By contrast, high-energy electron diffraction in transmission electron microscopy (TEM) can probe finite-sized crystals, though the measurement precision of unit-cell parameters is relatively poor for several practical reasons (Mugnaioli et al., 2009 Capitani et al., 2006 Hou & Li, 2008 ). However, their broad irradiation beam makes them ill-suited for probing finite-sized samples (Baer et al., 2008 ), especially those in the form of nanoscale materials (Shi, Zou et al., 2019 ), inclusions or precipitates in alloys (Antion et al., 2003 ), and structurally modulated materials that are multiphase such as multilayers and superlattices (Collier et al., 1998 ). X-ray and neutron diffraction are two well established methods for the unit-cell determination of single-phase materials. In a structural study, accurate measurement of unit-cell parameters for a crystalline phase is considered to be the first step towards identifying a crystalline phase with known structures (Pecharsky & Zavalij, 2003 Williams & Carter, 2009 Young, 1995 ) or solving the crystal structure of unknown crystals (Le Bail et al., 1988 David et al., 2006 ). Unit-cell parameters and symmetry elements are two fundamental crystallographic quantities for characterizing a crystal structure. Should the parallel-beam, nano-beam and convergent-beam modes of the TEM be used flexibly, the software can determine unit-cell parameters of unknown-structure crystallites (typically >50 nm). The feasibility of unit-cell determination of the TiO 2 nanorod using this package is also demonstrated. Using both simulated and experimental patterns, we detail the working procedure and address some effects of experimental conditions (diffraction distortions, misorientation of the zone axis and the use of high-index zone axis) on the robustness and accuracy of the software developed. Subsequently, the primitive cell can be reduced to the Niggli cell which, in turn, can be converted into the unit cell. The essence of the package is to reconstruct a 3D reciprocal primitive cell from a single electron diffraction pattern containing both zero-order Laue zone and high-order Laue zone reflections. Here, a new package for determining unit-cell parameters from a single electron diffraction pattern has been developed. Electron diffraction techniques in transmission electron microscopy (TEM) have been successfully employed for determining the unit-cell parameters of crystal phases, albeit they exhibit a limited accuracy compared with X-ray or neutron diffraction, and they often involve a tedious measurement procedure. ![]()
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