Structural transformation between two cubic phases of (NH4)3SnF7

(NH4)3SnF7 undergoes one reversible structural phase transition of the first order between two cubic modifications Pa−3 ↔ Pm−3m. The structural analysis has shown that octahedral SnF6 and tetrahedral NH4 groups are ordered in Pa−3 phase, while they are disordered in Pm−3m phase.