Ab initio Studies of the Structures and Energies of the H-(H2O) and H-(H2O)2 Complexes

摘要

Accurate calculations for the H-(H20) complex with extended basis sets are reported at the restricted Hartree-Fock (RHF) through the fourth-order Moller-Plesset (MP) perturbation levels of theory. In the equilibrium geometry of the H-(H2O) complex the H- anion is found to lie almost along one of the H-O bond directions. The H-H- distance proved to be very sensitive to electron correlation effects: it is 1.8 and 1.4 A at the RHF and MP2 levels, respectively. The interaction energy between H- and H20 at the MP4 level including counterpoise corrections for basis set superposition error, depending upon the basis set used, is found to range from 16.2 to 16.9 kcal/mol, and the electron correlation is responsible for one-third of this value. The enthalpyh of formation of H- (H2OL) is estimated to be from - 15.2 to -16.0 kcal/mol compared with the experimental value of -17.3 + or - 1.2 kcal/mol. The vibrational frequencies of H- (H20) are also reported. The H-(H20) complex is also studied by using a polarized double zeta basis set. The geometry of the H-(H20)2 complex is partly optimized at the MP2 level and the energetic effects of the addition of the second water to H-(H20) are analyzed. (Water, Hydrogen)