title: A Rietveld refinement method for angular- and wavelength-dispersive neutron time-of-flight powder diffraction data.
abstract: This paper introduces a two-dimensional extension of the well established Rietveld refinement method for modeling neutron time-of-flight powder diffraction data. The novel approach takes into account the variation of two parameters, diffraction angle 2θ and wavelength λ, to optimally adapt to the varying resolution function in diffraction experiments. By doing so, the refinement against angular- and wavelength-dispersive data gets rid of common data-reduction steps and also avoids the loss of high-resolution information typically introduced by integration. In a case study using a numerically simulated diffraction pattern of Rh0.81Fe3.19N taking into account the layout of the future POWTEX instrument, the profile function as parameterized in 2θ and λ is extracted. As a proof-of-concept, the resulting instrument parameterization is then utilized to perform a typical refinement of the angular- and wavelength-dispersive diffraction pattern of CuNCN, yielding excellent residuals within feasible computational efforts. Another proof-of-concept is carried out by applying the same approach to a real neutron diffraction data set of CuNCN obtained from the POWGEN instrument at the Spallation Neutron Source in Oak Ridge. The paper highlights the general importance of the novel approach for data analysis at neutron time-of-flight diffractometers and its possible inclusion within existing Rietveld software packages.
authors.affiliation: Chair of Solid-State and Quantum Chemistry, Institute of Inorganic Chemistry, RWTH Aachen University , Aachen, D-52056, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Jacobs
authors.affiliation: Chair of Solid-State and Quantum Chemistry, Institute of Inorganic Chemistry, RWTH Aachen University , Aachen, D-52056, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Houben
authors.affiliation: European Spallation Source ESS , Lund, SE-22100, Sweden ; Jülich Center for Neutron Science and Peter Grünberg Institute PGI, Forschungszentrum Jülich , Jülich, D-52425, Germany.
authors.forename: Werner
authors.initials: W
authors.lastname: Schweika
authors.affiliation: Chair of Solid-State and Quantum Chemistry, Institute of Inorganic Chemistry, RWTH Aachen University , Aachen, D-52056, Germany ; Department of Chemistry, and Poncelet Laboratory of Mathematics in Interaction with Physics and Informatics, Lomonosov Moscow State University, Independent University of Moscow, Moscow Center for Continuous Mathematical Education , Bolshoi Vlasevsky Per. 11, Moscow, 119002, Russian Federation.
authors.forename: Andrei L
authors.initials: AL
authors.lastname: Tchougréeff
authors.affiliation: Chair of Solid-State and Quantum Chemistry, Institute of Inorganic Chemistry, RWTH Aachen University , Aachen, D-52056, Germany.
authors.forename: Richard
authors.initials: R
authors.lastname: Dronskowski
keywords: POWGEN; POWTEX; Rietveld refinement; VITESS; angular-dispersive; neutron diffraction; powder methods; wavelength-dispersive