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The high-pressure elastic properties of celestine and the high-pressure behavior of barite-type sulphates
Yunqian Kuang, Jingui Xu, Dongyu Zhao, Dawei Fan, Xiaodong Li, Wenge Zhou and Hongsen Xie

The structural stability and elastic properties of celestine have been investigated at room temperature and pressure up to 15GPa, by using in situ angle-dispersive X-ray diffraction and a diamond anvil cell. No phase change is observed within the range of pressure in this study. Analysis of room temperature P-V data to a third-order Birch-Murnaghan (BM) Eos yields: the zero-pressure volume V0 = 306.0(6) Å3, isothermal bulk modulus K0 = 62(5) GPa and its pressure derivative K0 = 11(1). If K0 is fixed at 4, then the isothermal bulk modulus is K0 = 98(2) GPa. In addition, the axial compressiblity moduli of the three unit cell axes of celestine are obtained as Ka0 = 102(2) GPa, Kb0 = 92(2) GPa and Kc0 = 98(2) GPa, indicating the anisotropy of axial compressibility, with the a axis the most incompressible and the b axis the most compressible. Furthermore, the elastic properties of barite-type sulfates are discussed by combining the results in this study with previous studies on barite-group minerals.

Keywords: Celestine, High-pressure, X-ray diffraction, Diamond anvil cell, Equation of state

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