Jahn‐Teller distortion, octahedra rotations and orbital ordering in perovskites: KScF3$$ {}_3 $$ as a model system

Abstract

AbstractThe KScF perovskite has been used as a model for investigating the relative importance of the Jahn‐Teller (JT) lift of degeneracy, the ScF octahedra rotation (OR), and the quadrupole‐quadrupole interaction linked to different occupancy of the Sc t subshell in various sites of the unit cell (orbital ordering, OO). The group‐subgroup sequence , , , and , supplemented by and , has been explored by using an Gaussian type basis set, hybrid functionals, and the CRYSTAL17 code. The JT lift of degeneracy provides a stabilization about 5 times larger than the sum of the OO and OR effects. The energy gained in the transition from to , consisting in a rotation of the octahedra around the axis, is 1077 E. From to , additional rotations around the and axes are possible, and the Sc electron can occupy a different t orbital, with a total energy reduction of 2318 E. The rotation of the octahedra reduces the strength of superexchange: in going from to the G‐AFM stabilization with respect to FM shrinks by a factor 4.