MOLECULAR GEOMETRIES AND ENERGETICS OF METAL-CONTAINING SYSTEMS USINGAN IMPROVED ASED-MO MODEL - A SYSTEMATIC TEST TO GROUP-1 AND GROUP-2 METAL-CONTAINING SYSTEMS IN THE GAS-PHASE

Accurate potential energy curves for highly polar metal-containing sys tems of the group 1 and 2 metals have been calculated by an improved A SED-MO model. The major components of the improvements consist of the addition of an intramolecular Madelung-type potential to the Born-Oppe nheimer energy, accounting for the electrostatic attractive interactio ns between the charged atoms in the molecule and the usage of Slater-t ype orbital exponents dependent on the atomic net charges. The new com putational scheme has successfully been applied in predicting the stru ctural and energetic parameters of the whole series of the neutral and ionic (cationic and anionic) group 1 and 2 metal oxide diatomics in b oth their ground and selected low-lying electronic states, as well as the corresponding series of the metal monohydroxides. The importance o f the inclusion of the intramolecular Madelung-type potential for the satisfactory description of a highly ionic bonding has been demonstrat ed by applying the new theoretical model on the series of the ''unknow n'' molecule/dipole CH4.MO and CH4.MO(+) (M = Be, Mg, Ca, Sr and Ba) c omplexes involving both a highly ionic M-O and a very weak Van der Waa ls type CH4...MO interactions.