We carried out nonresonant inelastic x-ray scattering measurements at the V 𝐿₁ edge to probe the local V 3𝑑 harge density in VO₂ across the metal-insulator transition (MIT). Without relying on spectral calculations, we were able to integrate directly from the orientational dependence an image of the occupied 3𝑑 shell and extract quantitatively the orbital occupations of the V ions. We found that in the low-temperature insulating 𝑀1 phase the V is highly polarized toward the 𝜎 configuration. The orbital occupation undergoes significant redistribution upon transition into the metallic 𝑅 phase, leading to a more isotropic charge density. The massiveness of the orbital switching promotes the scenario in which electron correlations and lattice degrees of freedom are strongly coupled, so that the contribution of the lattice and the electronic part to the energetics must be treated on equal footing to model the MIT quantitatively.
Dolmantas et al. (Thu,) studied this question.