transition metal oxide perovskites

Epitaxial strain offers an effective route to tune the physical parameters in transition metal oxides. So far, most studies have focused on the effects of strain on the bandwidths and crystal field splitting, but recent experimental and theoretical works have shown that also the effective Coulomb interaction changes upon structural modifications. This effect is expected to be of paramount importance in current material engineering studies based on epitaxy-based material synthesization. Here, we perform constrained random phase approximation calculations for prototypical oxides with a different occupation of the d shell, LaTiO₃ (d¹), LaVO₃ (d²), and LaCrO₃ (d³), and systematically study the evolution of the effective Coulomb interactions (Hubbard U and Hund’s J) when applying epitaxial strain. Surprisingly, we find that the response upon strain is strongly dependent on the material. For LaTiO₃, the interaction parameters are determined by the degree of localization of the orbitals, and grow with increasing tensile strain. In contrast, LaCrO₃ shows the opposite trend: the interaction parameters shrink upon tensile strain. This is caused by the enhanced screening due to the larger electron filling. LaVO₃ shows an intermediate behavior.