Intriguing Structural Transition Inducing Variable Birefringences in ABa2MS4Cl (A = Rb, Cs; M = Ge, Sn)

A suite of quinary thiohalides, ABa2MS4Cl (A = Rb, Cs; M = Ge, Sn), have been successfully synthesized. ABa2MS4Cl (A = Rb, Cs; M = Ge, Sn) undergoes an interesting structural transition from P21/c (α phase) to I4/mcm (β phase), which also leads to obvious disparities on the birefringence from 0.041 (α phase) to 0.094 (β phase). Moreover, the result of deploying a real-space atom-cutting method on ABa2MS4Cl reveals that their (MS4)4– groups may take the major effect in terms of the anisotropy by a structural transition.