International Tables for Crystallography
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The optics and alignment of the divergent-beam laboratory X-ray powder diffractometer and its calibration using NIST standard reference materials International Tables for Crystallography (2019). Vol. H, ch. 3.1, pp. 224-251 [ doi:10.1107/97809553602060000946 ] Abstract The laboratory X-ray powder diffractometer is one of the primary analytical tools in materials science. It is applicable to nearly any crystalline material, and with advanced data-analysis methods, it can provide a wealth of information concerning sample character. Data from these machines, however, are beset by a complex aberration function that can be addressed through calibration with the use of NIST standard reference materials (SRMs). Laboratory diffractometers can be set up in a range of optical geometries; considered herein are those of Bragg–Brentano divergent-beam configuration using both incident- and diffracted-beam monochromators. We review the origin of the various aberrations affecting instruments of this geometry and the methods developed at NIST to align these machines in a first-principles context. Data-analysis methods are considered as being in two distinct categories: those that use empirical methods to parameterize the nature of the data for subsequent analysis, and those that use model functions to link the observation directly to a specific aspect of the experiment. We consider a multifaceted approach to instrument calibration using both the empirical and model-based data-analysis methods. The particular benefits of the fundamental-parameters approach are reviewed. |
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About International Tables for Crystallography
International Tables for Crystallography is the definitive resource and reference work for crystallography. The multi-volume series comprises articles and tables of data relevant to crystallographic research and to applications of crystallographic methods in all sciences concerned with the structure and properties of materials.