Abstract：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 $Pa\bar{3}$) is metastable under lower pressure. Insulating $I4/mcm$-ZnO$_{2}$ is thermodynamically stable between 128.3–300 GPa. Insulated metastable $P3_{1}21$-ZnO$_{2}$, controlling the pressure range of 51.5–128.3 GPa, has a wide band gap compared to the $Pa\bar{3}$-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.
2016, Vol. 33 
