Determination of physically based pseudo‐Voigt powder diffraction profile terms from the fundamental parameters approach. Issue 2 (11th March 2022)

• Record Type: Journal Article
• Authors: Denney, Jonathan J.; Mattei, Gerard S.; Mendenhall, Marcus H.; Cline, James P.; Khalifah, Peter G.; Toby, Brian H.
• Is Part Of: Journal of applied crystallography. Volume 55:Issue 2(2022)
• Page Start: 289
• Page End: 295
• Publication Date: 2022-03-11
• Subjects: powder diffraction -- fundamental parameters -- Rietveld analysis -- GSAS‐II; Crystallography -- Periodicals; 548.05
• DOI: 10.1107/S1600576722001169
• Languages: English
• ISSNs: 0021-8898

Abstract

Abstract : A novel mechanism is presented to derive GSAS‐II profile coefficients from a fundamental parameters description of an X‐ray powder diffractometer. This can be used for standard‐free determination of microstrain and crystallite size and has applications for machine learning. Abstract : A methodology is developed where a fundamental parameters approach (FPA) description of a laboratory powder diffraction instrument (configured in divergent‐beam Bragg–Brentano geometry) is used to determine GSAS‐II profile parameters for peak asymmetry and instrumental peak widths. This allows the instrumental contribution to peak shapes to be robustly determined directly from a physical description of the instrument, even though GSAS‐II does not directly implement FPA for peak shape computation. The FPA‐derived parameters can be used as the starting point for instrument characterization, or to characterize sample broadening without the use of a standard to determine the instrument profile function. This new method can facilitate generation of training sets for machine learning. A plot is generated that shows the differences between the two approaches, demonstrating upper bounds for the accuracy of the GSAS‐II profile model for a particular instrumental configuration.