In‐plane structure of ferecrystalline compounds

This work provides a review on the in‐plane structure of a recently established subgroup of misfit layer compounds, namely ferecrystals. While misfit layer compounds can be described as layered intergrowths of two distinct substructures in which only one axis of the subunits remains incommensurate, for ferecrystals both constituents retain independent in‐plane crystalline structures. This is accompanied by extensive rotational disorder, a key feature of ferecrystals. Our comparison of the in‐plane structures of misfit layer compounds and ferecrystals suggests that the weaker registration between the subunits in ferecrystals allows the synthesis of a wider variety of compounds, varying both the range of constituents, their mismatch and their thicknesses. The in‐plane structures of the individual constituents in ferecrystalline compounds exhibit interesting features such as 2D‐symmetry, size induced structural transformation, misfit parameters that depend on the component thicknesses, and pairing distortions of constituent layers.