Pressure-volume equation of state for chromite and magnesiochromite: A single-crystal X-ray diffraction investigation

The pressure-volume equation of state for the two spinel end-member compositions chromite FeCr2O4 and magnesiochromite MgCr2O4 was determined for flux-grown synthetic single crystals at room temperature up to 8.2 and 9.2 GPa, respectively, by single-crystal X-ray diffraction using a diamondanvil cell. The pressure-volume data show that the linear volume compressibility (here used only for purpose of comparison), calculated as beta(V) = vertical bar[Delta V/V-0)/Delta P]vertical bar, is 0.00468 and 0.00470 GPa(-1), for chromite and magnesiochromite, respectively, with a negligible difference below 0.5%. The experimental data were fitted to a third-order Birch-Murnaghan equation of state (BM3) allowing a simultaneous refining of the following coefficients: V-0 = 588.47(4) angstrom(3), K-T0 = 184.8(1.7) GPa, and K' = 6.1(5) for chromite and V-0 = 579.30(4) angstrom(3), K-T0 = 182.5(1.4) GPa, and K' = 5.8(4) for magnesiochromite. The difference in K-T0 is reduced to