by epitaxial constraints*

5d transition metal oxides provide an ideal playground where strong crystal field splitting encounters strong spin-orbit coupling. Here, using first principles density functional theory (DFT) calculations, we study the strain responses of the atomic structure and electronic properties in the correlated perovskite metal SrIrO₃. We examine the proposed breakdown of the J_eff states using DFT calculations compared with available experimental data. We find that although DFT and DFT+U methods qualitatively reproduce the iridate band structure, these methods result in incorrect orbital projections, which lead to ambiguity of the J_eff picture. Our results suggest that epitaxial strain is a useful way for tailoring the 5d spin-orbit coupling in perovskite iridates.