The Stable or Metastable Phases in Compressed Zn-O Systems

Variable-composition evolutionary structure searches are used to explore stable stoichiometries for the Zn-O system below 300 GPa. Our results confirm the previous structural phase transition sequence of pressurised ZnO. ZnO is thermodynamically stable up to 300 GPa and zinc peroxide (ZnO_2, space group Pa\bar3) is metastable under lower pressure. Insulating I4/mcm-ZnO_2 is thermodynamically stable between 128.3–300 GPa. Insulated metastable P3_121-ZnO_2, controlling the pressure range of 51.5–128.3 GPa, has a wide band gap compared to the Pa\bar3-ZnO_2 and I4/mcm-ZnO_2. Phonon and elastic constant calculations conclude the dynamical and mechanical stability for the explored thermodynamically stable or metastable structures.