Equation of state and compressibility of phlogopite by in-situ high-pressure X-ray power diffraction

The elastic properties of a natural phlogopite have been studied by in-situ high-pressure X-ray powder diffraction experiments on the ID9 beamline at the ESRF, at room temperature. Several EoS models (Birch-Murnaghan, Vinet, Poirier-Tarantola) have been fitted to the experimental P-V data and the results obtained are presented and discussed. The third order Birch-Murnaghan EoS, assuming V0 fixed at its experimental value, yields K0=49.7(±0.5) GPa, K0’=8.59(±0.19), K0’’= -0.5953 GPa-1 (implied value). The axial compressibilities at room conditions, determined by the third order Birch-Murnaghan EoS, result bEoSa0=3.48(5), bEoSb0=3.2(1), bEoSc0= 13.2(1) 10-3 GPa-1. Equilibrium thermodynamic calculations have been carried out to show how the new elastic parameters here reported affect the stability field of phlogopite.