Accurate structure refinement and measurement of crystal charge distribution using convergent beam electron diffraction

The method for accurate structure refinement from energy-filtered convergent-beam electron diffraction (CBED) patterns is described with emphasis on recent progress in using imaging filters and 2-D detectors. Details are given about the underlying theoretical model and the statistical analysis of experimental data. The relationship between crystal potential and charge density is also derived for crystals at thermal equilibrium. The method is applied to the refinement of Si (111) and (222) structure factors using various goodness-of-fit (GOF) criteria. Results show that the refinement method is robust and highly accurate. The importance of the experimentally measured structure factors is illustrated through the study of the charge density in MgO. With the measured structure factors, it is possible to obtain details about the charge redistribution due to crystal bonding.