Structure of Tl18Pb2Ti7S25 as a masterpiece of crystallographic symmetry

A crystallographic analysis of the cubic structure of Tl₁₈Pb₂Ti₇S₂₅ has established the arrangement of all cations and anions according to the law of the 27-fold (with respect to volume) structure type of PbS(NaCl) with strictly fixed anionic vacancies. The nonintersecting axes of symmetry (bar 3) of four directions organizing the structure distribute cations differing in sizes, charges, and amounts over general and particular sites of the sp. gr. Pa3 to form a high-symmetry design in the simple atomic matrix.