Refinamento de tamanho de partículas e microdeformação de amostras policristalinas através de perfis de difração de raios-x utilizando as teorias cinemática e dinâmica

Abstract

The instrumental broadening, systematically obtained by the use of a standard reference material profile can, in principle, be replaced by an analytical model of the instrumental broadening. For this purpose fast and stable computational routines must be developed to perform Fourier transforms, convolutions and least squares fitting, brand new technologies for parallel computing and graphics programming for visualization of data is now available, toolkits like Qt provide a way to create easy to use and visually appealing applications for structure refinement. On the other hand two theories exist to describe X-ray diffraction in crystals. The kinematical theory is simpler and provides good results for fine powders of imperfect crystals. The dynamical theory must be used for the treatment of diffraction in large perfect crystals and describes phenomena that are not explained by the kinematical theory. These two theories were used as models for refinement of crystallite size and lattice strain of two samples, one of them, a LaB6 SRM660 bought from NIST (National Institute for Standards and Technology), and the other a Cerianite (CeO2) synthesized at the LRX laboratory at the Federal University of Ceará using the protein sol-gel method and calcined in rotating oven. The program then developed was written in C++ on a GNU/Linux platform and is portable to other systems.