  Using the strongly constrained and appropriately normed (SCAN) and SCAN+U
approximations for describing electron exchange-correlation (XC) within density
functional theory, we investigate the oxidation energetics, lattice constants,
and electronic structure of binary Ce-, Mn-, and Fe-oxides, which are crucial
ingredients for generating renewable fuels using two-step, oxide-based, solar
thermochemical reactors. Unlike other common XC functionals, we find that SCAN
does not over-bind the O2 molecule, based on direct calculations of its bond
energy and robust agreement between calculated formation enthalpies of main
group oxides versus experiments. However, in the case of transition-metal
oxides (TMOs), SCAN systematically overestimates (i.e., yields too negative)
oxidation enthalpies due to remaining self-interaction errors in the
description of their ground-state electronic structure. Adding a Hubbard U term
to the transition-metal centers, where the magnitude of U is determined from
experimental oxidation enthalpies, significantly improves the qualitative
agreement and marginally improves the quantitative agreement of
SCAN+U-calculated electronic structure and lattice parameters, respectively,
with experiments. Importantly, SCAN predicts the wrong ground-state structure
for a few oxides, namely, Ce2O3, Mn2O3, and Fe3O4, while SCAN+U predicts the
right polymorph for all systems considered in this work. Hence, the SCAN+U
framework, with an appropriately determined U, will be required to accurately
describe ground-state properties and yield qualitatively consistent electronic
properties for most transition- metal and rare earth oxides.
