The (H2O)(2)CO ternary complex: cyclic or linear?

Optimal structures, interaction energies, and harmonic vibrational frequenc ies of the (H2O)(2)CO ternary complex have been determined from the supermo lecular calculations with the aug-cc-pVDZ and the aug-cc-pVTZ basis sets. E nergetic properties of the complex have been calculated at MP4 and CCSD(T) levels. We located three low-energy configurations on the potential energy surface corresponding to two isomeric H-bonded cyclic complexes and one lin ear structure. The tunneling motion of the water molecule across the plane of the heavy atoms ring was studied. The calculations of the vibrational fr equencies and infrared intensities for this complex are presented to facili tate the frequency assignments of future experimental spectra. (C) 2001 Pub lished by Elsevier Science B.V.