The high-pressure behaviour of the cubic phase of KPF6 – An X-ray single-crystal and entropy-maximization study

Abstract

Abstract The high-pressure behaviour of cubic KPF6 up to 0.40 GPa was studied using single crystal-diffraction techniques. The crystal structures at ambient conditions and at 0.15 GPa were investigated using maximum-entropy and Fourier methods. Even under pressure the PF6 octahedra are highly disordered but the electron-density distribution differs from that at ambient conditons. The cubic phase of KPF6 is highly compressible: The lattice parameter varies from a = 7.7813(3) Å at normal pressure to a = 7.7144(5) Å at 0.40 GPa. Whereas powder samples already transform at about 0.1 to 0.2 GPa into the highpressure phase KPF6, II, the transition pressure for single crystals is higher. The transition pressure depends not only on the crystal size but also on the crystal quality, and also time may play a role.