Pressure dependence of the elastic moduli of single crystal MgF2 to 1 GPa

This is the authors' abstract. We don't add key points for this paper.

The six independent elastic constants of a single crystal of tetragonal MgF2 with rutile structure were measured ultrasonically at room temperature from ambient conditions to 10 kbar. The values at 1 bar and 10 kbar are (in 1011 dyn/cm2) C11: 14.081 (1 bar), 14.597 (10 kbar); C12: 9.003 (1 bar), 9.569 (10 kbar); C13: 6.417 (1 bar), 6.543 (10 kbar); C22: 20.490 (1 bar), 21.094 (10 kbar); C44: 5.664 (1 bar), 5.768 (10 kbar); C66: 9.560 (1 bar), 9.964 (10 kbar). CS=(C11−C12)/2 softens with pressure, while C44 shows a weak pressure dependence. Similar behavior has been observed in NiF2, ZnF2, TiO2, and in the distorted rutile crystal TeO2. The reported pressure induced transition from tetragonal MgF2 to distorted fluorite type observed at 250 kbar using x-ray scattering is not anticipated by the softening of CS which would lead to an orthorhombic distortion.