Self-consistent site-dependent DFT+ U study of stoichiometric and defective SrMnO3

We propose a self-consistent site-dependent Hubbard U approach for density functional theory (DFT)+U
calculations of defects in complex transition metal oxides, using Hubbard parameters computed via linear
response theory. The formation of a defect locally perturbs the chemical environment of Hubbard sites in its
vicinity, resulting in different Hubbard U parameters for different sites. Using oxygen vacancies in SrMnO3 as
a model system, we investigate the dependence of U on the chemical environment and study its influence on
the structural, electronic, and magnetic properties of defective bulk and strained thin-film structures. Our results
show that a self-consistentU improves the description of stoichiometric bulk SrMnO3 with respect to generalized
gradient approximation (GGA) or GGA+U calculations using an empiricalU. For defective systems,U changes
as a function of the distance of the Hubbard site from the defect, its oxidation state, and the magnetic phase of
the bulk structure. Taking into account this dependence, in turn, affects the computed defect formation energies
and the predicted strain- and/or defect-induced magnetic phase transitions, especially when occupied localized
states appear in the band gap of the material upon defect creation.