  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.
