We describe the various methods wherein NIST SRMs may be used to discern sources of measurement error as well as properly characterize and calibrate instrument performance. The preferred method is to use National Institute of Standards and Technology, NIST, Standard Reference Materials, SRMs, to calibrate instruments in the field and qualify instrument performance. Therefore, the results are often somewhat diabolical and the origin of difficulty is problematic to discern. The task may be further compounded when instruments are set up incorrectly, as the resultant errors are convoluted into the already complex aberration set. Not all nanoscale particles can be approximated by spheres, and powder XRD data can look different for particles of the same. The inset shows the 1, 2, and 5 nm XRD patterns on an expanded y -axis scale for clarity. While advanced data analysis methods can be used to model the various aberrations and account for the observed profile shape and position, there are a number of instrumental effects about which there is insufficient knowledge for reliable, a priori modeling of instrument performance. Simulated powder X-ray diffraction patterns for wurtzite CdS spherical particles of different sizes that range from 1 m to 1 nm. ![]() Practical data collection rates can be realized with the use of a. A continuous suite of hkl reflections can be collected with a single scan in angular space. The use and development of extreme sample environments of temperature, magnetic field, and pressure. The laboratory X-ray powder diffractometer offers several virtues that have rendered it a principal characterization device providing critical data for a range of technical disciplines. With low angular coverage and a clean background, HB-2A is particularly well-suited to studying new, complex, magnetically ordered systems. However, a drawback exists in the context of the para-focusing optics of laboratory diffractometers which produce patterns that display profiles of a most complex shape. The Neutron Powder Diffractometer (HB-2A) a versatile instrument, able to examine a variety of materials. Furthermore, with more advanced data analysis methods a wealth of additional information may be discerned. These factors serve to permit timely qualitative analyses which are requisite for many applications. The sample format is typically comprised of finely divided crystallites that are compacted into a flat plate this format is amenable to a wide variety of materials. Practical data collection rates can be realized with the use of a divergent beam that can illuminate a large volume of diffracting crystallites. The full Powder Suite at ORNL, including HB-2A, is outlined in a recent Powder Suite article. ![]() The laboratory X-ray powder diffractometer offers several virtues that have rendered it a principal characterization device providing critical data for a range of technical disciplines. Instrument Overview: An article titled 'The high-resolution powder diffractometer at the high flux isotope reactor' details capabilities and specifications.
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