Compressibility of a natural smithsonite ZnCO3 up to 50GPa

Natural smithsonite (ZnCO3) has been investigated by synchrotron radiation X-ray diffraction and X-ray absorption spectroscopy combined with diamond anvil cells up to 50GPa at room temperature. At ambient pressure, smithsonite adopts as calcite phase with a=4.6557(11)angstrom and c=15.072(12)angstrom. Both experimental results demonstrate that no phase transition occurs in the present examined pressure range. Isothermal pressure-volume relationship of smithsonite can be well described by the third-order Birch-Murnaghan equation of state with V-0=284.6(7)angstrom(3), B-0=126.8(6)GPa and (fixed). The axial compressibility of smithsonite presents clear anisotropy with alpha(c)=3.60x10(-3)angstrom GPa(-1)>alpha(a)=1.21x10(-3)angstrom GPa (-1). ZnCO3-smithsonite is proposed to approach the NaCl rocksalt structure on compression.