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X-ray diffraction study of calcium-lead fluorapatite solid solution at high pressure: the composition dependence of the bulk modulus and its pressure derivative
Dawei Fan, Shuyi Wei, Jing Liu, Yanchun Li and Hongsen Xie
The compression behavior of a natural fluorapatite has been investigated to about 29.2 GPa at 300 K using in situ angle-dispersive X-ray diffraction and a diamond anvil cell at High Pressure Experiment Station, Beijing Synchrotron Radiation Facility (BSRF). The unit-cell parameters and volume decreased systematically with increasing pressure, and the isothermal equation of state was determined. The values of V0, K0, and K′0 refined with a third-order Birch-Murnaghan equation of state are V0 = 559.7 ± 0.8 Å3, K0 = 75 ± 5 GPa, and K′0 = 5.6 ± 0.7. Furthermore, we obtained that the axial compressibilities of the natural fluorapatite [3.97(8) * 10-3 GPa-1 and 3.12(6) * 10-3 GPa-1 for the a– and c-axis, respectively]. In addition, combining with previous results, the compositional dependence of the bulk modulus and its pressure derivative are discussed.
Keywords: Synchrotron, X-ray diffraction, Equation of state, fluorapatite, high pressure.