Finally, the [METALLOID]-centered hexagonal planar geometry is similar to the distorted one. The pentagonal planar geometry is obtained by reducing a vertex, and its distorted one is ranked next, the hexagonal pyramidal geometry by adding a vertex to the planar geometry comes to the next with a distortion, the bipyramidal geometry with another vertex comes to the next. These geometric concepts are certainly similar. For Sm 2 CoMnO 6 , all the structures have similar compositions and structures. All of them are structured in orthorhombic perovskite derivatives except for Sm 2 RuCoO 6 , which also seems to have quite a similar structure.