Vanadium energy bands

The magnetic moment arising from the ground A term is expected to be close to the spin-only value of 3.87 BM and independent of temperature. In practice, providing the compounds are mononuclear, these expectations are realized remarkably well apart from the fact that, as was noted for octahedral complexes of vanadium(lll), the third high-energy band in the spectrum is usually wholly or panially obscured by more intense chaige-transfer absorption. 

F ure 11.2 Energy bands for vanadium along the line A F H) of the first Brillouin zone obtained from two different potentials (a) bands resulted from an atomic configuration of 3d 4s (b) bands that involved a 3d 4s atomic configuration (after [32]). 

VP Zhukov, VA Gubanov, O Jepsen, NE Christensen, OK Andersen. Calculated energy-band structures and chemical bonding in titanium and vanadium carbides, nitrides and oxides. J Phys Chem Sohds 49 841, 1988. 

There is considerable repulsion energy involved in this transition, since an electron must be moved from a delocalized ir orbital into an occupied b2 orbital which is localized on the vanadium. This repulsion energy is estimated as ca. 11,700 cm.-1 by comparing the positions of the first charge transfer band of VOa+ with the first band of VO-Cla.21 This 11,700 cm.-1 estimate is included in the predicted energy for the B2 - 2E(II) transition. Both the predicted energy and the predicted / value agree wdl with the experimentally observed values. 

All binding energies reported have been corrected for charging by comparing the location of the Cls bands with that for A1 2p. Correction of the A1 2p band to 74.7 eV coincided with peak fitting of the C Is bands in which a prominent carbon peak was within 0.3 eV of the ubiquitous C Is assumed to be at 284.6 eV. Hence, peak positions for vanadium were corrected using the A1 2p at 74.7 eV. 

Band gap energies, nature of vanadium surface species... 

As shown in Fig. 8, the vibrational bands are clearly resolved in the photoluminescence spectrum of vanadium oxide supported on Vycor glass 33, 34, 36-38). The vibrational separation of about 1040 cm is in good agreement with the energy of the V=0 stretching vibration of the ground state of the vanadyl group of the oxide as measured by IR or Raman spectroscopies. 

Figure 20 shows the second-derivative spectrum of the photolumincs-cence shown in Fig. 19. The well-resolved fine structure indicates that the energy gap between the (0 -> 0) and (0 - 1) vibrational transition bands is 1040 cm in good agreement with the vibrational energy of the surface V=0 bond obtained by IR or Raman measurements. These findings indicate that the photon energy absorbed by the vanadium oxide/SiOa catatyst is mainly localized on the V=0 surface bonds.The Raman spectrum of the anchored vanadium oxide/Si02 catalyst observed at 78 K exhibits a peak at 1050 cm in good agreement with the results obtained by Went...

The electronic stmcture of bulk vanadium oxides is determined to a major extent by the amount of d electron occupation in the vanadium ions. In the ideal three-dimensional periodic bulk, electrons are described by Bloch states with energy dispersions reflected in band stmctures and corresponding densities of states (DOS). These quantities can be calculated with high accuracy by modem band stmcture and total energy methods based on the density functional theory (DFT) method. 

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