Ab initio potential energy surface and microwave spectra for the H2-HCCCN complex.

Abstract

We present a four-dimensional ab initio potential energy surface of the H2-HCCCN complex at the coupled-cluster singles and doubles with noniterative inclusion of connected triples [CCSD(T)]-F12 level with a large basis set including an additional set of bond functions. The artificial neural networks method was extended to fit the intermolecular potential energy surface. The complex has a planar linear global minimum with the well depth of 199.366 cm-1 located at R = 5.09 Å, φ = 0°, θ1 = 0°, and θ2 = 180°. An additional planar local minimum is also found with a depth of 175.579 cm-1 that is located at R = 3.37 Å, φ = 0°, θ1 = 110°, and θ2 = 104°. The radial discrete variable representation/angular finite basis representation and the Lanczos algorithm were employed to calculate the rovibrational energy levels for four species of H2-HCCCN (pH2-HCCCN, oH2-HCCCN, pD2-HCCCN, and oD2-HCCCN). The rotational frequencies and spectroscopic parameters were also determined for four complexes, which agree well with the experimental values.