Solution of phase problem for crystallography at a wavelength of 3.5 Å

Abstract

It has been established¹ that one viable method for determining phases in a diffraction experiment is to make use of multiple beam-diffraction, that is, a situation in which two or more reflections are excited simultaneously in a crystal. While the theory had been fully developed and tested in some experiments on a germanium crystal¹, progress was halted by the recognition that such theory could only be applied to perfect crystals such as germanium and silicon, with no mosaic structure. Here we report that considerable progress has been made, to the point of being able now to determine phases of structure factors in the most general situations, with non-centrosymmetric, small mosaic crystals of arbitrary shape. An example will be described here in which the phase of the (202) reflection of an organic molecular crystal (benzil) has been determined.