Calculation of bond distances, one-electron energies and electron density distributions in first-row tetrahedral hydroxy and oxyanions

The tetrahedral hydroxyanions $T(OH)4n$ and oxyanions of the first row elements from Li to N are studied using the ab initio SCF MO method. Equilibrium T–O distances calculated using small orbital basis sets are within 0.05Å of their average values in solids so long as the charge on the anion is small. One electron orbital energies from larger basis set calculations on the oxyanions are used to interpret the valence region photoemission spectrum of BeO and to predict the spectral characteristics of tetrahedral B, C and N. Contour maps of the difference in electron density between molecular cluster and superimposed spherical neutral atoms show features which can be qualitatively interpreted in terms of ionic or covalent bonding.