Crystal structure analysis of the orthorhombic phase II of KLiSO4

Abstract The crystal structure of the orthorhombic high-temperature phase II (708–949 K) of KLiSO 4 was analyzed by single-crystal neutron diffraction. The ambiguity concerning the symmetry of this phase is solved and a disordered structure is established in the space-group Pcmn. Hence, KLiSO 4 II is confirmed to be isostructural to the highest-temperature modification I of RbLiSO 4 .The investigated KLiSO 4 crystals were pseudohexagonally twinned with three ferroelastic domain states according to the phase transition from P6 3 (phase III at room temperature) to Pcmn (phase II).