Structures of [001] twist boundaries in gold. I. Measurement and use of absolute boundary x-ray structure factors

Abstract

An x-ray-diffraction method for measuring absolute grain-boundary structure factors is described. The method is based on ratioing appropriate integrated scattered intensities from the grain-boundary region and from the adjoining perfect-crystal region in a bicrystal specimen containing a flat grain boundary. Common unknown factors then cancel out, and an expression for the absolute structure factor is obtained in which all quantities are either known, can be measured, or can be calculated with acceptable accuracy. A practical experimental technique for making the necessary measurements, which employs a four-circle diffractometer, is described. The technique is applied to an x-ray diffraction study of the atomistic structures of a series of [001] twist boundaries in gold in the following paper of our work. The results obtained there clearly demonstrate that the measurement of absolute structure factors, rather than relative structure factors, provides important information in diffraction studies of the structures of grain boundaries, particularly in cases where a limited number of structure factors is measured.