The microstructure - covering aspects related to the coherently scattering domains and their defects - deeply influences the properties, and thus the functionality of a material. In an X-ray powder diffraction pattern, the information on the microstructure is usually extracted from the breadth and shape of line profiles. The Whole Powder Pattern Method (WPPM)1 is the most advanced self-consistent technique for the microstructural analysis of materials, able to provide e.g. quantitative information on size, shape, size distribution, dislocations in traditional materials. In some cases, the features observed in the pattern (such as odd profile shapes, deeply anisotropic line profile broadening, diffraction bands) can witness an intimate interplay between structural and microstructural features that cannot be modelled via WPPM. An alternative LEGO-type modelling is proposed: the global structure is described in terms of simple objects stacked via a probabilistic approach. Through the use of the DIFFaX+ software2, structure, microstructure and stacking parameters can be refined from powder diffraction data. Traditional, defective, layered, ordered/disordered, modular structures showing a local or global reduction of the lattice symmetry due to the presence of defects can be analysed in this way. Basics and examples of both methods will be shown and commented 1Scardi, P.; and Leoni M., Acta Cryst. A 2004, 190-200. 2Leoni, M.; Gualtieri A.F.; Roveri N., J. Appl. Cryst. 2004, 37, 166-173.
Structure, microstructure and LEGO crystallography
Leoni, Matteo
2010-01-01
Abstract
The microstructure - covering aspects related to the coherently scattering domains and their defects - deeply influences the properties, and thus the functionality of a material. In an X-ray powder diffraction pattern, the information on the microstructure is usually extracted from the breadth and shape of line profiles. The Whole Powder Pattern Method (WPPM)1 is the most advanced self-consistent technique for the microstructural analysis of materials, able to provide e.g. quantitative information on size, shape, size distribution, dislocations in traditional materials. In some cases, the features observed in the pattern (such as odd profile shapes, deeply anisotropic line profile broadening, diffraction bands) can witness an intimate interplay between structural and microstructural features that cannot be modelled via WPPM. An alternative LEGO-type modelling is proposed: the global structure is described in terms of simple objects stacked via a probabilistic approach. Through the use of the DIFFaX+ software2, structure, microstructure and stacking parameters can be refined from powder diffraction data. Traditional, defective, layered, ordered/disordered, modular structures showing a local or global reduction of the lattice symmetry due to the presence of defects can be analysed in this way. Basics and examples of both methods will be shown and commented 1Scardi, P.; and Leoni M., Acta Cryst. A 2004, 190-200. 2Leoni, M.; Gualtieri A.F.; Roveri N., J. Appl. Cryst. 2004, 37, 166-173.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione
