Structure of caesium disulfate at 120 and 273 K
Abstract
The crystal structures of Cs2S2O7 at 120 and 273 K have been determined from X-ray single-crystal data. Caesium disulfate represents a new structure type with a uniquely high number of independent formula units at 120 K: In one part caesium ions form a tube surrounding the disulfate ions, Cs8(S2O7)6+n; in the other part a disulfate double-sheet sandwiches a zigzagging caesium ion chain, Cs2(S2O7)6-n. Caesium disulfate shows an isostructural order-disorder transition between 230 and 250 K, where two disulfate groups become partially disordered above 250 K. The Cs+-ion arrangement shows a remarkable similarity to the high-pressure RbIV metal structure.