Chemical reaction at high temperature and high pressure VI : polymorphic transition in ZnP2 at high temperature and high pressure

A new pressure-induced modification of zinc-diphosphide, ZnP_2, has been prepared by the direct union of zinc with phosphorus and also through the polymorphic transitions of both monoclinic and tetragonal ZnP_2. The application of pressures above 20kb combined with temperatures above 150℃ is required for the synthesis. The new modification of ZnP_2 has a pseudo-cubic crystal symmetry with a lattice constant a=5.322Å and has a measured density 3.55g/cm^3. It is found to be a semiconducting phase with an energy gap Eg=0.44eV at 15kb in the temperature range from 20° to 150℃. The effects of temperature and pressure on the polymorphic transition of monoclinic and tetragonal ZnP_2 have been investigated and the stability region for the high pressure modification determined by quenching method. The synthesis of a diamond-like form of ZnP_2, which is one of II-V_2type compounds, suggests the possibility of synthesizing other unsymmetrical group IV analogs which was predicted by Hall and Compton earlier.