The HCO+–H2 van der Waals interaction: Potential energy and scattering

Abstract

We compute the rigid-body, four-dimensional interaction potential between HCO(+) and H2. The ab initio energies are obtained at the coupled-cluster single double triple level of theory, corrected for Basis Set Superposition Errors. The ab initio points are fit onto the spherical basis relevant for quantum scattering. We present elastic and rotationally inelastic coupled channels scattering between low lying rotational levels of HCO(+) and para-/ortho-H2. Results are compared with similar earlier computations with He or isotropic para-H2 as the projectile. Computations agree with earlier pressure broadening measurements.

Modelling Vibrational Dissociation of [H2–HCO]+

“…The results of the plane‐wave calculations (with a MT basis set) are in a reasonable agreement in both E int and ▵E ZPE from the Gaussian‐orbital calculations. However, both DFAs overbind the complex by up to 10 kJ/mol compared to our CP–MP2/CBS+δ(T) results at the respective minima, and by up to 13 kJ/mol compared to the previous correlated wavefunction theory results . For comparison, the E int at the optimised geometry obtained with a state‐of‐the‐art single‐hybrid DFA (ωB97M‐V) is within 2.5 kJ/mol of the CP‐MP2/CBS+δ(T) result.…”

“…The interaction energy obtained with the latter is comparable to the QCISD(T) data of Bieske et al . This contrasts with the later study of Massó and Wiesenfeld, where no such stationary point was found …”

“…From comparison with the fully‐relaxed results, the fixed monomer approximation introduces an error of ∼ 0.45 kJ/mol in E int . These small energy differences are unlikely to be responsible for the difference in the stationary points on the reported [H 2 –HCO] + PESs …”

“…Therefore, in the current work, we investigate the dynamics of vibrationally activated dissociation of the complex using ab initio molecular dynamics (AIMD) and density functional theory (DFT). First, the uncertainty due to the density functional approximation (DFA) is estimated by a comparison to symmetry adapted perturbation theory (SAPT) as well as wavefunction theory (WFT) calculations performed on the system, and to the most relevant regions of the high‐accuracy CP‐CCSDT/CBS potential surface of Massó and Wiesenfeld . The complex is then investigated dynamically, by comparison to experimental spectra, and by a mode‐selective vibrational excitation.…”

“…[10] The [D 2 -DCO] + complex has also been studied experimentally. [11] The most recent investigation of the [H 2 -HCO] + complex is the theoretical study by Massó and Wiesenfeld, [12] who reported a detailed potential energy surface (PES) of interaction energies (E int ) using a counterpoise-corrected coupled cluster method including full triples, with basis set extrapolated to the complete basis set limit (CP-CCSDT/CBS).…”