A case study of parameterized Rietveld refinement:The structural phase transition of CuInSe2

Abstract

Abstract The ferroelastic high temperature structural phase transition of CuInSe2, from tetragonal chalcopyrite to cubic sphalerite structure type has been reinvestigated in detail by sequential and parametric Rietveld refinement using in-situ high energy synchrotron powder diffraction data. For the description of the structural changes, a symmetry mode based approach is used. The temperature dependence of the isotropic displacement parameters and of all symmetry modes influencing lattice parameters, atomic coordinates, and occupancies, has been modeled with a phenomenological power law model according to the Lanädau theory in order to get direct access to the temperature dependence of the order parameter leading to a more detailed understanding of the nature of the phase transition. The results of this study reveal superior statistics and much higher stability of parametric as compared to sequential Rietveld refinement, offering exciting possibilities in the analysis of ferroelastic phase transitions.