Polymorphic Control of CsGaE2 (E = S, Se) Using Diorganyl Dichalcogenide Precursors.

Diorganyl dichalcogenides (R-E-E-R, where R = organyl and E = S, Se, Te) are employed for the polymorphic control of diamond-like crystal structures, due to their tunable C-E bond reactivity. In this work, we extend their application to non-close-packed alkali-metal-based chalcogenides by demonstrating the selective synthesis of CsGaE2 (E = S, Se) polymorphs. Weaker C-E bonds or higher temperatures promote the formation of the thermodynamically stable mC64 phases, while stronger C-E bonds or lower temperatures allow for the isolation of the metastable mC16 phases. Heat-treatment studies reveal the pronounced metastability of CsGaSe2-mC16 particles and the irreversible phase transition of CsGaS2 analogous to its bulk counterpart.