Crystallographic Analysis and Symmetry Generation for Some Structures with [As₂] and [Hg _n] (n = 2, 3) Cluster Groups

The crystallographic analysis of the structures of [Hg₇As₄](AgI₃)₂ (I), [Hg₆As₄Br₃](SnBr₃) (II), and [Hg₁₁As₄](GaBr₄)₄ (III) treated as host-guest structures is performed. It is shown that the spatial basis (“skeleton”) of the structures is formed by crystallographic planes densely occupied by mercury and halogen atoms. The cubic symmetry of the first two structures is initiated by the local symmetry of the ([As₂]Hg₆) building block. The C2/m symmetry of the third structure is initiated by the 2/m local symmetry of the blocks with linear groups containing [Hg₂] and [Hg₃] fragments.