A stoichiometrically conserved homologous series with infinite structural diversity.

We describe a compositionally guided structural evolution within a stoichiometrically conserved framework, BaSbQ3 (Q = Te1−xSx), where each value of x gives rise to a distinct phase. The fundamental building blocks, A1 (BaSbSTe2) and Bn (BanSbnSn−1Te2n+1), were composed of modular double rocksalt slabs stacked with functional polytelluride zigzag chains, with each phase differing only in the size and assembly of these blocks. Ten compounds were synthesized that maintained a coherent chemical identity that arose from this isovalent, isoelectronic substitution of Te and S. We envision that the phase formation at a molecular level unfolds in stages of extension, termination, and assembly and propose a design concept of "anionic disparity," where phase homologies and polytelluride hierarchical networks can be controlled by leveraging differences in anion electron affinity and sizes. Editor's summary: A series of BaSbQ3 crystals (where Q is sulfur or tellurium) has been synthesized, and its structural diversity is directly driven by systematically varying the S/Te ratio. Zhao et al. synthesized at least 10 of these "stoichiomorphs" composed of rocksalt slab fragments stacked together with polytelluride zigzag chains. Each member differed only in the size and assembly of these blocks, and the crystal phase that resulted depended on differences in anion electron affinity and sizes. —Phil Szuromi [ABSTRACT FROM AUTHOR]