First-principles study of ground- and metastable-state properties of XO (X = Be, Mg, Ca, Sr, Ba, Zn and Cd)

The ground- and metastable-state properties of II-VI oxides in wurtzite (h-MgO), zincblende and rocksalt structures are systematically investigated using first-principles. We study the phase stability of these three structures energetically, and find that CaO, SrO and BaO prefer h-MgO instead of wurtzite. This is consistent with the fact that ionic compounds prefer a high coordination. We also examine the influence of the crystallographic structure and cations on elastic constants, bulk moduli, spontaneous polarisation, piezoelectricity, band structures and optical properties. The band offsets for the common semiconductors (BeO, MgO, ZnO and CdO) in the zincblende structure are calculated. Our calculated results are in good agreement with other theoretical and experimental data.