Negative charge transfer ABO3 oxides may undergo electronic metal--insulator transitions (MIT) concomitant with a dilation and contraction of nearly rigid octahedra. On both sides of the MIT are in-phase or out-of-phase (or both) rotations of adjacent octahedra that buckle the B--O--B bond angle away from 180∘. Using density functional theory with the PBEsol+U approach, we describe a novel octahedral engineering avenue to control the B 3d and O 2p orbital polarization through enhancement of the BO6 rotation "sense" rather than solely through conventional changes to the B--O bond lengths, \emph{i.e.} crystal field distortions. Using CaFeO3 as a prototypical material, we show the flavor of the octahedral rotation pattern when combined with strain--rotation coupling and thin film engineering strategies offers a promising avenue to fine tune orbital polarizations near electronic phase boundaries.
@article{arxiv.1304.0982,
title = {Octahedral Engineering of Orbital Polarizations in Charge Transfer Oxides},
author = {Antonio Cammarata and James M. Rondinelli},
journal= {arXiv preprint arXiv:1304.0982},
year = {2015}
}