Polysynthetic Twinning in RbIn3S5

The real structure of the new ternary compound RbIn3S5 is characterized by polysynthetic twinning of nanosized domains separated by coherent twin boundaries. Based on electron microscopy, a model of the structure at the twin interface is derived which allows a convincing simulation of experimental images. The details of twinning are described in a unified model. As a rule, a disordered arrangement of twin lamellas with a random distribution of their widths is observed with ordering of twin boundaries only in nanosized regions of the crystallites. For a minimal distance of the twin boundaries (back-to-back twinning) the close relationship between twinning and shearing is discussed. The distinction of these two cases is only possible by close inspection of the atomic structure at the boundaries. Twinning is not the only crystal defect in the structure of RbIn3S5. Variations in the connection of the characteristic structural units occur which lead to the formation of different real structures.