GROUND AND EXCITED-STATE PROPERTIES OF THE CATIONIC AND ANIONIC FIRST-ROW TRANSITION-METAL OXIDE DIATOMICS CALCULATED BY AN IMPROVED ASED-MO MODEL

The performance of an improved atom superposition and electron delocal ization molecular orbital (ASED-MO) model has been investigated for th e ground and selected low-lying excited states of the entire sequence of the highly-polar cationic and anionic first-row transition-metal ox ide diatomics. In particular, in both series of compounds deep potenti al energy curves of an almost Morse-type shape were derived allowing f or an adequate calculation of the equilibrium geometries, bond dissoci ation energies, as well as other spectroscopic constants. With some ex ceptions, values derived are in good agreement with both the experimen tal and theoretical ones, where available, whereas in the case of the anions most values derived are predictive theoretical ones appearing f or the first time. The variation of the M-O bond strengths, ionization potentials, electron affinities and hardness along the sequences of t he cationic and anionic species follow the ''double humped'' pattern, characteristic of many periodic properties of the transition metals. T he calculated ground states for both series of compounds are also disc ussed. Present results, along with our earlier findings for the neutra l MO molecules, provide a further confirmation of the good performance of our ASED-MO variant in the case of transition-metal oxide diatomic s. (C) 1997 Elsevier Science B.V.