Structural Implications of Spin, Charge, and Orbital Ordering in Rubidium Sesquioxide, Rb4O6

Abstract

Abstract Rb4O6 displays mixed valency on the anionic lattice and an open p‐shell electronic configuration. At ambient conditions, it exists in a disordered ground state structure, featuring three different potential ordering parameters related to phase transitions driven by charge, orbital and spin ordering. The possible paths of symmetry descent are analyzed by elaborating the respective group‐subgroup relations between space groups, including the implications that would result from magnetic ordering. Experimentally, a lower symmetry modification was discovered and characterized by single‐crystal X‐ray diffraction [I$\bar{4}$, Z = 4, a = 8.688(6), c = 10.362(7) Å, R1 = 0.055, 787 independent reflections]. The symmetry reduction involved follows one branch of the Bärnighausen tree as predicted, I$\bar{4}$3d → I$\bar{4}$2d → I$\bar{4}$ convincing evidence was obtained for Rb4O6 undergoing charge and orbital ordering, along with respective structural order.