Evolutionary Algorithm-Based Crystal Structure Prediction of Cu(x)Zn(y)O(z) Ternary Oxides

Binary zinc(II) oxide (ZnO) and copper(II) oxide (CuO) are used in a number of applications, including optoelectronic and semiconductor applications. However, no crystal structures have been reported for ternary Cu-Zn-O oxides. In that context, we investigated the structural characteristics and thermodynamics of Cu(x)Zn(y)O(z) ternary oxides to map their experimental feasibility. We combined evolutionary crystal structure prediction and quantum chemical methods to investigate potential Cu(x)Zn(y)O(z) ternary oxides. The USPEX algorithm and density functional theory were used to screen over 4000 crystal structures with different stoichiometries. When comparing compositions with non-magnetic Cu(I) ions, magnetic Cu(II) ions, and mixed Cu(I)-Cu(II) compositions, the magnetic Cu(2)Zn(2)O(4) system is thermodynamically the most favorable. At ambient pressures, the thermodynamically most favorable ternary crystal structure is still 2.8 kJ/mol per atom higher in Gibbs free energy compared to experimentally known binary phases. The results suggest that thermodynamics of the hypothetical Cu(x)Zn(y)O(z) ternary oxides should also be evaluated at high pressures. The predicted ternary materials are indirect band gap semiconductors.