Spectral momentum densities of vanadium and vanadium oxide as measured by high energy (e, 2e) spectroscopy

The spectral momentum densities of vanadium metal and V₂O ₃ are measured by electron momentum spectroscopy. Results are compared with band structure calculations based on density functional theory (DFT). Qualitatively, the agreement between theory and experiment is good. The calculated total band width of vanadium metal (6.5 eV) is in excellent agreement with the observed one (6.5 ± 0.25 eV). The splitting between the outer and inner valence bands in V₂O₃ is 2 eV larger in the experiment than in the density functional theory calculation. The observed momentum distributions agree reasonably well with the calculated distributions with the exception of the intensity of the outer valence band relative to the inner valence band in V₂O₃: the outer valence band is less intense than calculated. The momentum density near the Fermi level in V metal resembles that of atomic V 3d orbitals. However, momentum profiles of the V 3d orbitals in V₂O₃ are much more sharply peaked than the atomic 3d orbital in both the theory and experiment. Correlation effects are discussed and theoretical problems in describing EMS data from narrow band systems are identified.