Low-order structure-factor amplitude and sign determination of an unknown structure AlmFe by quantitative convergent-beam electron diffraction

An iterative method for the determination of structure-factor amplitudes and phases of crystals with unknown structure is proposed. The method is based on the quantitative evaluation of energy-filtered convergent-beam electron diffraction (CBED) patterns. It has been applied to the metastable phase AlmFe (m = 4.2-4.4), which was found as primary particles in commercial aluminium alloys. When the rocking curves of reflections along a (100) systematic row are fitted, a number of structure-factor amplitudes and signs of h00-type reflections of AlmFe have been determined successfully. The accuracy of the structure-factor amplitudes is better than 5% for the strong reflections and about 10% for the weak reflections. The aim of this method is to provide accurate structure-factor data, including both amplitudes and phases, for ab initio structure determination and refinement of unknown structures by using electron diffraction techniques.