Ab initio potential energy surface and microwave spectra for Kr-NCCN complex

The potential energy surface of Kr-NCCN complex is obtained and its microwave spectra are predicted using ab intio method. [Display omitted] •The characteristics of potential energy surface for Kr-NCCN complex are described.•The microwave spectra of Kr-NCCN complex are investigated.•The spectroscopic constants of Kr-NCCN complex are obtained based on the calculated rotational energy levels. Ab initio potential energy surface of Kr-NCCN complex has been investigated using the coupled-cluster singles and doubles with noniterative inclusion of connected triples [CCSD(T)], which including two mixed basis sets, aug-cc-pvDz for the C and N atoms, and aug-cc-pvDz-pp for the Kr atom, containing the midbond function of 3s3p2d1f1g. The potential energy surface of Kr-NCCN complex has a T-shaped global minimum locating at R = 6.96 a0, θ = 90° with the energy of −281.677 cm−1, the two equivalent local minima with the energy of −123.513 cm−1 locating at the linear geometry for R = 10.70 a0, and two saddle points between the global and the two local minima are located at R = 10.61 a0, θ = 10.1° and 169.9° with V = −123.304 cm−1, respectively. The bound state energies up to J = 9 for Kr-NCCN are calculated based on the potential energy surface by solving the Schrödinger equation, and the microwave transition frequencies are also investigated. Finally, the calculated spectroscopic constants are obtained based on the calculated rotational energy levels. These results could provide a theoretical basis for the experimental spectra research of Kr-NCCN complex.