Obtaining models suitable for Rietveld refinement: the EXPO2011 techniques
-
Angela Altomare
Abstract
Rietveld refinement succeeds if the model is sufficiently close to the target structure. Severe distortions in the structural parameters or relatively high percentage of missed atoms do not allow the refinement to converge. Ab initio techniques like Direct or Patterson methods may rely only on the reflection intensities provided by full pattern decomposition algorithms. Owing to the relevant errors in the intensity estimates, the structural models provided by such phasing techniques are poor and require supplementary improvements before being submitted to Rietveld refinement. The situation is more favorable for non-ab initio techniques, when they can exploit the prior information on the full molecular geometry: their models can be easily submitted to Rietveld refinement, but often the accuracy of the refined model relies on the geometrical information rather than on the experiment. In this paper ab initio and non-ab initio phasing tools of EXPO2011, the updated and more powerful version of EXPO2009 [1], are described together with ancillary techniques for improving and completing the structural models.
© by Oldenbourg Wissenschaftsverlag, Bari, Germany
Articles in the same Issue
- Preface: Modern Rietveld Analysis
- Preface: Modern Rietveld Analysis
- Obtaining models suitable for Rietveld refinement: the EXPO2011 techniques
- Complex inorganic structures from powder diffraction:case of tetrahydroborates of light metals
- Recent developments targeting new and experienced users in EXPGUI, an open source Rietveld analysis interface
- Testing different methods for estimating uncertainties on Rietveld refined parameters using SrRietveld
- Understanding anisotropic microstrain broadening in Rietveld refinement
- On the modelling of the powder pattern from a nanocrystalline material
- Rietveld refinement of energy-dispersive synchrotron measurements
- Description and survey of methodologies for the determination of amorphous content via X-ray powder diffraction
- A case study of parameterized Rietveld refinement:The structural phase transition of CuInSe2
Articles in the same Issue
- Preface: Modern Rietveld Analysis
- Preface: Modern Rietveld Analysis
- Obtaining models suitable for Rietveld refinement: the EXPO2011 techniques
- Complex inorganic structures from powder diffraction:case of tetrahydroborates of light metals
- Recent developments targeting new and experienced users in EXPGUI, an open source Rietveld analysis interface
- Testing different methods for estimating uncertainties on Rietveld refined parameters using SrRietveld
- Understanding anisotropic microstrain broadening in Rietveld refinement
- On the modelling of the powder pattern from a nanocrystalline material
- Rietveld refinement of energy-dispersive synchrotron measurements
- Description and survey of methodologies for the determination of amorphous content via X-ray powder diffraction
- A case study of parameterized Rietveld refinement:The structural phase transition of CuInSe2
