Electronic structure and magnetic properties of Ca2IrO4, using first principles

It is well known that when Coulomb potential is expressed in terms of electron density, the unphysical self-interaction term is not completely canceled in the semi-local approximations such as LDA. Hence, these approximations tend to stabilize the artificially delocalized electronic states, since such effects tend to reduce the self-repulsion of electrons. In many cases, such effects tend to incorrectly capture the insulating state, or even render a metallic state. Moreover, a simple formalism that serve corrections to pitfalls in the LDA prescription is the mBJ formalism. In the latter, a screening term of the form t/ρ is introduced to the exchange potential, the contribution of which is calculated by |∇|/ρ. Here, t and ρ represent the kinetic-energy density and electron density, respectively. As a consequence, regions with low density are associated with higher positive potential thereby increasing the energy of the unoccupied states.149