First Principles Band-gap Calculations of 3d Transition Metals-added ZnO

The band-gaps of rock salt Zinc Oxide added with 3d transition metals (TM = Mn, Fe, Co, Ni) are estimated by Density Functional Theory (DFT) as implemented in the WIEN2k code. The Full Potential Linearized Augmented Plane Wave (FP-LAPW) method, within the Local Density Approximation (LDA) and the Generalized Gradient Approximation (GGA) is employed, in order to find band-structures of Zn1-X(TM)XO alloys at x = 25%, 50%, and 75%. The results show metallic nature for all TM-doped ZnO alloys, contrary to the semiconducting nature as predicted by the experimentalists. This reveals an inadequacy of simple LDA and GGA schemes for band-gap calculations of highly correlated systems as in our case.