Prediction of subgap states in Zn- and Sn-based oxides using various exchange-correlation functionals

Abstract

We present a density-functional-theory analysis of crystalline and amorphous Zn- and Sn-based oxide systems which focuses on the electronic defect states within the band gap. A comparison of these electronic levels reveals that the hybrid functionals PBE0, HSE06, or B3LYP agree with a self-interaction corrected (SIC) local-density-approximation functional on occupied defect levels when similar treatments of the self-interaction are considered. However, for unoccupied levels, the hybrid functionals and the SIC approach lead to very different predictions. We show that a prerequisite for the determination of the energetic position of subgap states in these oxides is that a functional needs to predict correctly the electronic band structure over a wide energy range and not just close to the band gap. We conclude that for accurate defect levels, an adequate treatment of the self-interaction problem is required especially in the presence of nearby metal-metal interactions.Financial support for this work was provided by the European Commission through Contract No. NMP3-LA-2010-246334 (ORAMA). The calculations at Cambridge were performed using the High Performance Computing Facility, Darwin, and also the UK national high performance computing service ARCHER, for which access was obtained via the UKCP consortium and funded by EPSRC Grant No. EP/K014560/1.Phys. Rev. B 90, 195142 – Published 21 November 2014 ©2014 American Physical Society, http://dx.doi.org/10.1103/PhysRevB.90.19514