Pressure induced wurtzite-to-zinc blende phase transition in ZnO at finite temperature

We predict a possible phase transition of ZnO from wurtzite to zinc blende structure using first-principles molecular-dynamics simulations. By calculating the Gibbs free energies of the two phases as a function of temperature and hydrostatic pressure, we show that their energy difference decreases continuously with increasing temperature and pressure, and the vibrational entropy plays an important role on the location of the phase transition point. At 300 K, the phase transition is expected to occur at a pressure lower than 30 GPa with an activation energy barrier of 0.386 eV/atom. The transition path was also simulated, along which the system goes through a transient face-centered orthorhombic structure to overcome the energy barrier. Our theory results may be valuable for stabilizating the zinc blende ZnO in experiment.