COMPARISON BETWEEN AB-INITIO AND DENSITY-FUNCTIONAL CALCULATIONS IN THE REACTION )+H-2((1)SIGMA(+)(G))-]OH+((3)SIGMA(-))+H(S-2)((S)

The reaction between O+ and H-2 has been studied by means of density f unctional methods. We adopt a combined procedure in which a Hartree-Fo ck, or GVB-PP calculation, is complemented by the calculation of the c orrelation energy using a density functional. Four different correlati on functionals are used: Perdew's (PF), Becke's (BF), and the more rec ent ones of Moscardo and San-Fabian (MSF), and Moscardo and Perez-Jime nez (MP). We have also carried out Kohn-Sham calculations combining di fferent exchange-correlation functionals. The functionals MSF and MP, together with the GVB-PP wave function, provide the best numerical res ults. Bond lengths, dissociation energies, and the more difficult to o btain category the reaction energy,compare favorably with the result o f very extensive MRC1-MP2 calculations. (C) 1998 Elsevier Science B.V.