Electronic structure of vanadium dioxide: Ab initio density functional theory studies of periodic and local systems

The electronic structure of vanadium dioxide in its monoclinic and tetragon al (rutile) phase are calculated using, the ab initio FP-LAPW method. Both VO2 phases yield very similar band structures and densities of states (DOS) as expected from their structural similarity. A comparison of theoretical band dispersions of tetragonal VO2 with recent angular resolved photoemissi on data yields very good agreement, which confirms the reliability of the F P-LAPW method to account for electronic dispersions in the present systems. The calculations yield metallic behavior for both VO2 phases in-contrast t o experimental findings of the monoclinic phase being a small gap semi-cond uctor. This discrepancy is explained by missing correlation contributions i n the density functional theory (DFT) scheme used in the calculations. The DOS curves of the bulk systems are compared with the DOS of VO2(011) surfac e clusters obtained by DFT calculations and yield very close similarity in the O 2p band region without surface specific features which remains to be explained.