Compressibility of a natural smithsonite ZnCO₃up to 50 GPa

Abstract

Natural smithsonite (ZnCO3) has been investigated by synchrotron radiation X-ray diffraction and X-ray absorption spectroscopy combined with diamond anvil cells up to 50 GPa at room temperature. At ambient pressure, smithsonite adopts as calcite phase with a=4.6557(11) Å and c=15.072(12) Å. 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 V0=284.6(7) Å3, B0=126.8(6) GPa and (fixed). The axial compressibility of smithsonite presents clear anisotropy with αc=3.60×10−3 Å GPa−1>αa=1.21×10−3Å GPa −1. ZnCO3-smithsonite is proposed to approach the NaCl rocksalt structure on compression.