Pressure-volume-temperature equation of state of andradite and grossular, by high-pressure and -temperature powder diffraction

The thermoelastic parameters of natural andradite and grossular have been i nvestigated by high-pressure and -temperature synchrotron X-ray powder diff raction, at ESRF, on the ID30 beamline. The P-V T data have been fitted by Birch-Murnaghan-like EOSs, using both the approximated and the general form . We have obtained for andradite K-0 = 158.0(+/-1.5) GPa, (dK/dT)(0) = -0.0 20(3) GPa K-1 and alpha (0) = 31.6(2) 10(-6) and for grossular K-0 = 168.2( +/-1.7) Gpa, (dK/dT)(0) = -0.016(3) GPa K-1 and alpha (0) = 27.8(2) 10(-6) K-1. Comparisons between the present issues and thermoelastic properties of garnets earlier determined are carried out.