High pressure behavior of mercury difluoride (HgF2)

[Display omitted] •First reported experimental XRD study of HgF2 at high pressure up to 63 GPa.•Discovery of a ramp pressurization purification technique for HgF2.•Discovery of phase transition near 5 GPa. EOS in both phases agrees with theory. The pressure-induced cubic → orthorhombic transition occurring in HgF2 was investigated via X-ray diffraction and density functional theory. The predicted, ambient cubic (Fm-3m) fluorite structure of HgF2, can be obtained using a high-pressure ramp purification process of HgF2 mixed with XeF2. Subsequently, the purified HgF2 underwent a phase transition from the fluorite to the orthorhombic cotunnite-type structure near 4.7 GPa, persisting to 63 GPa. An equation of state fit yielded a bulk modulus K0 of 94.4 GPa for the fluorite-type structure and zero-pressure volume V0 of 168.6 Å3, and K0 = 92.9 GPa and V0 = 156.4 Å3 for the cotunnite-type structure.