Single-crystal to single-crystal phase transition with a large deformation in Zn(OH)2 under high-pressure

High-pressure behavior of Zn(OH)2 with a techto-silicates related structure was investigated under hydrostatic condition by X-ray diffraction method for both powdered and single-crystal specimens. A quick single-crystal to single-crystal transition was discovered at 1.1 GPa. The transition occurred with 10% volume change and a large deformation in the sharp. The high-pressure phase has an α-cristobalite related structure, in which ZnO4 tetrahedrons build up a three-dimensional framework. To explain all these facts a simple displacive mechanism by tilting ZnO4 tetrahedrons is proposed for the transition.