Insulator-to-metal transition in Bi₂Ru₂O₇ pyrochlores: role of the uncorrelated Bi off-centering

Understanding the insulator-to-metal transitions (IMT) in complex oxides is of fundamental interest both from the theoretical and applicative point of view.

Here, using density functional theory calculations, we investigate the IMT in the oxide pyrochlore Bi₂Ru₂O₇.  Our results suggest the combination of primary and secondary (due to size) electronic effects of the lone pair-driven incoherent cation displacements are responsible for the metallic state of pyrochlores with Bi substitution.