Stable phase with the type structure in under high pressure and high temperature

High-pressure and high-temperature behavior of MgF2 was observed up to 15 GPa and 750 ∘C by an in-situ X-ray diffraction method. The single phase with the α-PbO2 type structure was obtained at 12.7 GPa and 750 ∘C. The phase was almost quenchable to ambient condition. Its orthorhombic cell parameters were a 0 = 4.590 ( 1 ) Å , b 0 = 5.555 ( 1 ) Å and c 0 = 5.048 ( 1 ) Å and its volume per chemical formula was 1.1% smaller than that of the rutile phase at ambient condition. MgF2 was confirmed to have a stable region for the phase at around 13 GPa and 600 ∘C and to have the rutile–CaCl2–α-PbO2–PdF2 type phase transition series under high pressure and high temperature, as predicted by a previous theoretical calculation method. The bulk modulus of the α-PbO2 type phase was determined to be K 0 = 98.0 ( 7 ) GPa .