Non-local screening channels and metal-insulator transition in VO2
  We studied the changes in the electronic structure of VO2 across the metal-insulator transition. The main technique was cluster model calculations with non-local screening channels. The calculation included a screening from a delocalized state at the Fermi level in the metallic phase, and a screening from the neighboring V site within the V-V dimmer in the insulating phase. Both the coherent and incoherent features in the V 3d band of metallic VO2 are well screened states, whereas the true poorly screened 3d0 state appears deeper in energy due to the relatively large U. The non-local screening state in the insulating phase involves U and consequently appears at higher energies. The change in the non-local screening channel opens the band gap originating the insulating phase. 
R.J.O. Mossanek and M. Abbate