High pressure phase transformations in MgF2 (rutile)

Employing a diamond-anvil pressure cell and a YAG laser as a heating source, phase relationships in polycrystalline MgF2 (rutile) were investigated to ∼330 kbar at both room temperature (∼23°C), and high temperature (∼1300°C). In situ high pressure X-ray diffraction data show that MgF2 (I) of rutile structure transforms into MgF2(II) of a cubic structure at ∼300 kbar at room temperature, and at ∼190 kbar at high temperature (∼1300°C), resulting in a negative dP/dT slope for the univariant line between MgF2(I) and MgF2(II) in the P-T phase diagram. The molar volume differences at room temperature between MgF2(I) and MgF2(II) at 190 kbar and 300 kbar are ∼8% and ∼5%, respectively.

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