VIBRATIONAL FREQUENCIES OF THE HF DIMER FROM THE COUPLED-CLUSTER METHOD INCLUDING ALL SINGLE AND DOUBLE EXCITATIONS PLUS PERTURBATIVE CONNECTED TRIPLE EXCITATIONS

Dissociation energies, equilibrium structures, equilibrium dipole moments, harmonic vibrational frequencies, infrared (IR) intensities, and zero-point vibrational energies (ZPVEs) are presented for the hydrogen fluoride monomer and dimer at the coupled cluster with single and double excitations plus perturbative connected triple excitations [CCSD(T)] level of theory with a series of large basis sets. Discussion focuses on the results from the largest basis set, triple zeta plus double polarization and one set of higher angular momentum functions [TZ2P(f,d)]. The structural parameters and dissociation energy agree well with the recent theoretical values reported in a high level ab initio study by Peterson and Dunning [J. Chem. Phys. 102, 2032 (1995)] and with experimental results. Here, the harmonic vibrational frequencies and IR intensities for the dimer are also predicted. The predicted vibrational frequency shifts relative to the monomer for the HF and DF stretching coordinates in the dimer are close to the experimental estimates. (C) 1995 American Institute of Physics.