High-Pressure Experimental and DFT Structural Studies of Aurichalcite Mineral

We report on high-pressure angle-dispersive synchrotron X-ray diffraction data of a natural Zn3.78(2)Cu1.22(2)(CO3)2(OH)6 aurichalcite mineral up to 7.6 GPa and ab initio total energy calculations the structure with three different Zn-Cu stoichiometries (Zn:Cu ratios = 10:0, 8:2 6:4). A monoclinic-to-triclinic displacive second-order phase transition was found experimentally at 3 GPa. The experimental bulk modulus initial P21/m is B0 66(2) GPa, first-pressure derivative B0′ 9(2). comparison other basic copper zinc carbonates shows that this value considerably larger than those malachite azurite. This relative incompressibility occurs despite fact features layered due number directed hydrogen bonds between carbonate groups cation-centered oxygen polyhedra forming complex sheets. existence bond types polyhedral compressibilities entails certain anisotropic compression, axial κa0 3.79(5)·10−3 GPa−1, κb0 5.44(9)·10−3 GPa−1 κc0 4.61(9)·10−3 GPa−1. Additional density-functional theory C2/m hydrozincite-type Zn:Cu compositional energetically more stable hydrozincite one for compositions 6:4 room pressure. pure Zn phase, however, predicted transform into 18 which suggests observed metastable phase.