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High-pressure investigation on prehnite: X-ray diffraction and Raman spectroscopy
Qian Zhang, Fei Qin, Jingjing Niu and Xiang Wu

The compression behavior of a natural sample of prehnite has been investigated using in situ angle-dispersive X-ray diffraction (XRD) and Raman spectroscopy combined with diamond anvil cell up to 25 GPa at room temperature. The results from XRD show that prehnite is stable with orthorhombic phase up to highest pressure, but a change of the axial compressiblities occurs at about 12 GPa. The results from Raman spectroscopy demonstrate discontinuity at about 11 GPa. Both experiments reveal a change of tetrahedral distortion at about 11-12 GPa. Parameters of isothermal equation of state of prehnite are V0=477.6±1.7 Å3, B0=103.5±5.0 GPa. Axial compressibility of prehnite presents obvious anisotropy. The Grüneisen parameters of prehnite are obtained according to its bulk moduli and the behavior of nine observed Raman modes.

Keywords: Prehnite, High pressure, Structural stability, Equation of state, X-ray diffraction, Raman spectroscopy

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