Geometry optimizations are carried out for the CN-H_2O, CN -H_2O, N0-H_20, NO -H_20, H0-H_20, and OH~-H_2O intermolecular complexes on both the uncorrected and CP-corrected potential energy hypersurfaces. Because of the correction of the BSSE during the gradient optimization, CP-corrected gradient optimization is more prior than normal optimization in structure research. But there is no significant difference between CP-corrected gradient optimization and normal optimization at interaction energies and BSSE. The diffusive basis functions are necessary for all the present systems. 6-311 ++ g** basis set is efficient to these systems for its good results with low time consumption. These radicals and anions all can form hydrogen bonding with H_2O. In the order of OH ~- , CN ~- , NO ~ -, OH, CN, NO, the interaction force changes from strong to weak. The same results can be obtained by analysis of interaction energy △E, the electron densityρof critical points, and the stabilization interaction energies E(2) .

Key words: INTERACTIONS, HYDROXY GROUP, NITRO-OXY RADICAL, CYANO GROUP, POTENTIAL ENERGY SURFACES