Cluster model for lattice distortion effects on electronic structure: VO and VO2

Molecular cluster predictions for electronic energy levels, wave functions, momentum densities, and Compton profiles of VO and V${\mathrm{O}}_2$ are examined within the Hartree-Fock-Slater model. V${\mathrm{O}}_6$ clusters are treated in $O_h$ $D_{4h}$ and $D_{2h}$ symmetry to obtain quantitative relations between distortion parameters and level shifts and splittings. Effects of the crystal environment are taken into account by a potential field. Our results for VO are consistent with the augmented plane-wave band calculation of Mattheiss and x-ray emission data; the V${\mathrm{O}}_2$ levels are in good agreement with x-ray photoelectron spectroscopy data. A sizable anisotropy is predicted for the Compton profile of VO and V${\mathrm{O}}_2$.