Simultane winkel- und wellenlängenabhängige Rietveld-Methodik für die Neutronenbeugung
| Autor: | Jacobs, Philipp |
|---|---|
| Přispěvatelé: | Dronskowski, Richard, Englert, Ullrich |
| Jazyk: | němčina |
| Rok vydání: | 2017 |
| Předmět: | |
| Zdroj: | Aachen 1 Online-Ressource (157 Seiten) : Illustrationen, Diagramme (2017). doi:10.18154/RWTH-2017-06584 = Dissertation, RWTH Aachen University, 2017 |
| DOI: | 10.18154/rwth-2017-06584 |
| Popis: | RWTH Aachen University, Diss., 2017; Aachen, 1 Online-Ressource (157 Seiten) : Illustrationen, Diagramme(2017). = RWTH Aachen University, Diss., 2017 In this work the fundamental aspects of a new simultaneous analysis of angular and wavelength dispersive (e. g. two-dimensional) neutron diffraction data have been worked out. To allow an optimized analysis of such two-dimensional data a new coordinate system consisting of variables d and d⊥ has been derived. Due to the coordinates being orthogonal, this special coordinate system is especially beneficial for the description of the reflection profile. With the additionally derived mathematical calculation rules an easy transformation between the different coordinates used for the analysis (e. g. 2θ, λ, d and d⊥) is possible. Based on this coordinate system an optimizes binning scheme for the originally event based data sets has been deduced, such that the bin size in both dimensions has no negative effect on the reflection profile and the resulting number of data points is optimized for a computer-based analysis. Simultaneously, the density of data points for the whole diffraction pattern was adapted to the varying reflection width. This ensures a uniform weighting of the different reflections during the Rietveld refinement as well as a better description of the reflection profile. Using data set obtained by the above-mentioned methods a parameterization of the profile parameters needed for the neutron time-of-flight diffractometers POWTEX and POWGEN has been derived. Due to the different reflection-profiles a different number of parameters had to be parameterized as a function of 2θ, λ and/or d. With the obtained parameters, a Rietveld refinement of two-dimensional data sets has been conducted for both instruments. To this end, distinct functions and scripts were implemented in the MATLAB and MANTID software packages to allow for a rudimentary Rietveld refinement. The advantages of this ansatz are a better description of the reflection profile as well as the course of the reflections. Additionally, angular and wavelength-dependent corrections (absorption, extinction, etc.) can be applied in more straightforward fashion. One of the key aspects is the fundamental description of the resolution function which is now based on physical properties of the instrument. Published by Aachen |
| Databáze: | OpenAIRE |
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