Time dependence of dislocation arrays in ice during recrystallization

Small-angle x-ray scattering (SAXS) from growing ice crystals shows sharp diffraction peaks at varying angles of reflection. The peaks have low intensities and rise and fall with a relaxation time of 100 to 1000 sec. The small widths point to superstructures with well defined dimensions. A quantitative analysis shows that these dimensions conform to the distances in coincident site lattices that are generated by two hexagonal ice lattices slightly rotated with respect to one another. It is concluded that the sharp SAXS reflections are caused by arrays of edge dislocations in small angle grain boundaries that develop during the growth of ice crystals and disappear during the recrystallization process.