Ab Initio SCF-SDCI Prediction of Type II Spectra and Geometry of (ClHCl)− Hydrogen Bond Complex. I. One Dimensional Vibrational Analysis

Abstract

Abstract Ab initio SCF(self-consistent field)-SDCI(single and double configuration interaction) calculations are presented on HCl2−. Applied basis sets are 4-31G, 4-31G(**) (no 3d-polarization functions on Cl atoms and 2p-polarization functions on H atom), 4-31G** (addition of polarization functions both on Cl and H atoms) and the split basis by Dunning (Cl/12s9p)(H/4s)→[Cl/6s5p][H/2s] with the addition of diffuse functions and/or polarization functions. Vibrational and geometrical analyses are performed on the Cl–Cl potential surface under symmetry conservation, and then on the proton potential surface at optimized RCl–Cl position. After potential interpolation by the continuous quadratic functions which reconstruct the calculated potential values on all mesh points, the quantal vibrational analysis is perfomed by the Störmer-Levy difference method. Discussion is made on the experimental confusion about the assignment of type II spectra of HCl2− as v3 mode in an argon matrix by the selection of basis set and of CI matrix expansion. Whereas the calculations in a primitive size proposes the double minimum potential surface of proton and type II spectra in ≈700cm−1 region as v3 (which corresponds to the experimental data by Evans and Lo (1966) and Ault (1975)), the extended calculations (i.e. the large basis sets and the great number of CI matrix expansion) reduce the central barrier of the proton potential and then conclude the IR absorption in 1000–1100 cm−1 region as v3 in the type II spectra (which corresponds to the experimental results of CsCl·1/3 [H3O+HCl2−] by Schröder (1970) and Smith (1973)).