Structural stability and electronic properties of Ba2MIrO6 (M = La, Y) by first principles

We investigate the structural stability and electronic properties of ordered perovskite-type compounds Ba2MIrO6 (M = La, Y) by use of density functional theory. Cubic (Fm-3m), rhombohedral (R-3) and monoclinic (P21/n) phases are considered for each compound. It was found that the most energetically stable phase for Ba2YIrO6 and Ba2LaIrO6 is P21/n and R-3, respectively. It is also interesting to find that Ba2YIrO6 in R-3 phase, which was not reported in experiment, has a slightly lower energy than experimentally observed cubic Fm-3m phase. The calculated results also show that Ba2YIrO6 in Fm-3m, R-3 and P21/n phases and Ba2LaIrO6 in Fm-3m phase are half metallic, while Ba2LaIrO6 in R-3 and P21/n phases show semiconducting behavior. The calculated spin magnetic moments indicate that the pentavalent iridium ion has a low spin configuration (t2g4) both in Ba2YIrO6 and Ba2LaIrO6