Accurate ab initio spectroscopic and thermodynamic properties of BBrx and HBBrx (x=0,+1,-1)

The near-equilibrium potential energy functions (PEFs) of BBr, its ions, BB r+ and BBr-, and HBBr and its ions, HBBr+ and HBBr-, have been determined u sing the singles and doubles coupled cluster method including a perturbatio nal correction for connected triple excitations, CCSD(T), together with sys tematic sequences of correlation consistent basis sets. A wide range of spe ctroscopic constants have been derived from the calculated PEFs as a functi on of basis set, including results obtained at the extrapolated complete ba sis set (CBS) limit. After the explicit inclusion of relativistic and core- valence correlation effects, the agreement with the available experimental values is excellent at the CCSD(T)/CBS level of theory. Accurate prediction s for the spectroscopic constants of the ions are made. The 0 K adiabatic i onization potentials and electron affinities are predicted to be (in kcal/m ol) 224.8, 4.3 (BBr) and 172.8, 22.2 (HBBr). The 0 K proton affinity of BBr is calculated to be 203.7 kcal/mol, while DeltaH(f)(0)(0 K) of BBr and HBB r are predicted to be 62.3 and 51.1 kcal/mol, respectively. The dipole mome nts and infrared intensities of the ions are calculated to be relatively la rge, which should facilitate their characterization by experimental methods . (C) 2001 American Institute of Physics.