COUPLED-CLUSTER CALCULATIONS OF THE POTENTIAL-ENERGY SURFACES AND SPECTROSCOPIC CONSTANTS OF SIF2, PF2-, AND CLO2+(, SO2, PO2)

Three dimensional near-equilibrium potential energy surfaces fro the 3 2-electron C-2 nu triatomics Sif(2), PF2+, PO2-, and ClO2+ have been c alculated using the coupled cluster method with single and double subs titutions augmented by perturbative treatment of triple excitations [C CSD(T)] with a basis set of 169 contracted Gaussian-type orbitals (cGT Os). A complete set of rotation-vibrational spectroscopic constants fo r each species has been calculated using second-order perturbation the ory formulas. The CCSD(T) equilibrium geometries of PF2+, PO2-, and Cl O2+ are r(2) = 1.505 Angstrom, theta(3) = 102.6 degrees, r(3) = 1.506 Angstrom, theta(e) = 118.9 degrees, and r(e) = 1.425 Angstrom, theta(e ) = 120.8 degrees, respectively. The calculated fundamental frequencie s (nu(a), nu(2), nu(3)) are 1017.8, 411.3, 1058.4 cm(-1) (PF2-), 1059. 7, 460.5, 1212.7 cm(-1) (PO2-), and 1005.1, 496.1, 1271.7 cm(-1) (ClO2 +). Dipole moments of these species have been calculated at each of th e CCSD(T) equilibrium geometries to predict microwave intensities. (C) 1996 American Institute of Physics.