Publication Date:
2014-07-02
Description:
The pressure-volume equation of state for the two spinel end-member compositions chromite FeCr 2 O 4 and magnesiochromite MgCr 2 O 4 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 diamond-anvil cell. The pressure-volume data show that the linear volume compressibility (here used only for purpose of comparison), calculated as β V = |[( V / V 0 )/ P ]|, 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) Å 3 , K T0 = 184.8(1.7) GPa, and K' = 6.1(5) for chromite and V 0 = 579.30(4) Å 3 , K T0 = 182.5(1.4) GPa, and K' = 5.8(4) for magnesiochromite. The difference in K T0 is reduced to 〈1.5% going from Fe to Mg end-member composition, whereas the first pressure derivative seems not to be affected by the chemical variability. The limited difference in the equation of state coefficients recorded for FeCr 2 O 4 and MgCr 2 O 4 allowed us to fit the pressure-volume data of both to a single BM3 equation, resulting in a K T0 = 184.4(2.2) GPa and K' = 5.7(6).
Print ISSN:
0003-004X
Electronic ISSN:
1945-3027
Topics:
Geosciences
