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Mineralogical ClassificationCrystalline structure investigation and high-pressure behavior of impurity-free siderite

26th Sep 2018 05:49 UTCMarco E. Ciriotti Manager

Reference:

▪ Liang, W., Yin, Y., Li, Zem., Li, R., Li, L., He, Yu, Dong, H., Li, Zen., Yan, S., Zhai, S., Li, H. (2018): Single crystal growth, crystalline structure investigation and high-pressure behavior of impurity-free siderite (FeCO3). Physics and Chemistry of Minerals, 45, 831-842.

Abstract:

Single crystals of impurity-free siderite were grown successfully using high-temperature–pressure annealing. The size of crystals ranged up to 100 µm, and they exhibited a rhomboid shape upon cleavage along the (101) plane. The composition of Fe0.9988±0.0011CO3 was quantified using electron probe analysis. Accurate crystalline structural data were investigated by means of single crystal X-ray diffraction (XRD) and the unit cell dimensions obtained in the rhombohedral symmetry of the R3¯c space group were a = 4.6861(3) and c = 15.362(2), and the final R = 0.0499. Using in situ synchrotron XRD, the high-pressure behavior of impurity-free siderite was investigated up to 20 GPa at ambient temperature. The pressure–volume (P–V) EoS was fitted by a third-order Birch–Murnaghan equation, and the isothermal bulk modulus was K0 = 97.5(11) GPa for K0′ = 4. High-pressure Raman spectroscopy was performed at up to 30 GPa at ambient temperature, and the Raman bands shifted as the increase of pressure (dνidP) was determined. In combination with the high-pressure Raman results and the bulk modulus K0, the mode Grüneisen parameters of each vibration were calculated. Meanwhile, high-temperature Raman spectroscopy was carried out at up to 300 °C and the Raman band shift (dνidt) was also quantified.