Effect of electron correlation and scalar relativistic corrections on the thermochemical and spectroscopic properties of HOF

Bond dissociation energies for the HOF system and an anharmonic force field for HOF are obtained from ab initio energies at the CCSD(T)/CBS level of theory, where the complete basis set (CBS) limit energies are obtained by extrapolating CCSD(T)/aug-cc-pVnZ (n = 2,3,4) energies. The effects of including core-valence correlation and scalar relativistic effects on the thermochemical and spectroscopic properties are investigated. The results are compared to available experimental results including recent re-evaluations of the properties of OF and OH. Quartic force fields are calculated at each level of theory and basis set used. Excellent agreement between experimental and calculated properties is obtained in most cases, but a few prominent and large differences in rotation-vibration coupling constants and a few force constants are observed. In these cases, our results are consistent with other, high level, ab initio evaluations of these properties. Given the ability of large basis set CCSD(T) calculations to yield accurate results for a wide range of molecular parameters, these differences suggest that experimental results may benefit from re-examination in some cases. A new recommendation for the 0 K enthalpy of formation of HOF, ∆ H f,0K = –20.02 ± 0.25 kcal/mol, is presented based on a careful analysis of recent experimental data and is supported by the high level ab initio calculations presented in this work