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

Abstract

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 V 0 fixed at its experimental value, yields K 0 = 49.7(±0.5) GPa, K’ 0 =8.59(±0.19), K’ 0 =-0.5953 GPa −1 (implied value). The axial compressibilities at room conditions, determined by the third-order Birch-Murnaghan EoS, result in β EoS a0 =3.48(5), β EoS b0 =3.2(1), β EoS c0 =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.