The performance of various GGA and LDA based mixed and improved exchange-correlation functionals for ZnO and ZnO:Mn: A first principles study

The performance of various LDA and GGA based mixed and improved exchange-correlation functionals is investigated by comparing their prediction for the electronic band structure, density of states and optical conductivity of pristine and Mn substituted ZnO structures. All the employed functionals display nearly similar trends but different numerical values for mentioned quantities which arises from their unique constraints. Our results show that mixed 05-95 functional widens ZnO band-gap by about 83 and 18% with respect to LDA and GGA, respectively. For the ZnO:Mn structure, this enhancement is about 15 and 4%, respectively. When exchange contribution reaches 85% in the mixed functionals, LDA + U concludes the same results with LDA. Among improved functionals, BLYP concludes the widest band-gap and LDA + U, along with PW92, predicts the highest conductivity in both structures. All functionals predict the same energy for O-2p state in the core region but different energies for Zn-3d and O-2p states. (C) 2020 Elsevier B.V. All rights reserved.