Glide planes symmetry in the organization of some sulfide structures

Resumo

The role of glide planes in the organization of structures is shown based on a crystallographic analysis of the monoclinic structures of TlAs₃S₅ and Tl₂(As,Sb)₃S₁₃ sulfides. In the first structure, cations and anions form systems (with identical geometries) of two face-centered sublattices, linked by the c plane, with the effect of unified “two-dimensional” (2D) ordering. The second structure, exhibiting signs of order–disorder (OD) type, is interpreted as a superposition of two noncentrosymmetric components with independent cation and anion sublattices, which, however, also form a regular 2D order due to the n plane. The stabilizing role of Tl cations in the geometry of cation matrices is indicated.