Cation order control of correlations in double perovskite Sr2VNbO6

Double perovskites extend the design space for new materials and they often host phenomena that do not exist in their parent perovskite compounds. Here we present a detailed first-principles study of the correlated double perovskite Sr2VNbO6, where the intercationic charge transfer and strength of electronic correlations depend strongly on the cation order. By using density functional theory + embedded dynamical mean field theory, we show that this compound has a completely different electronic structure than either of its parent compounds despite V and Nb being from the same group in the Periodic Table. We explain how the electronic correlations' effect on the crystal structural parameters determines on which side of the Hund's metal-Mott insulator transition the material is. Our results demonstrate the emergence of Hund's metallic behavior in a double perovskite that has d1 parents and underline the importance of electronic correlation effects on the crystal structure.