Theoretical study on potential energy surface and bound states of the Kr-CNCN complex: Compared with the Kr-NCCN system

The first ab initio potential energy surface of the Kr-CNCN system is investigated using the single double excitation coupled-cluster theory with noniterative treatment of triple excitation. The mixed basis sets are used with aug-cc-pVTz for the C and N atoms and aug-cc-pVTz-pp for the Kr atom, including an additional midbond function of 3s3p2d1f1g. The computed single point energies at 585 configurations are fitted to an analytical potential model. The potential energy surface of the Kr-CNCN complex has a nearly T-shaped global minimum with the energy of -286.6 cm(-1) located at R = 6.88 a(0), theta = 89.3 degrees. The interaction of the linear C-N-C-N-Kr geometry is stronger than that of the linear Kr-C-N-C-N structure. The whole potential energy surface of the Kr-CNCN presents angular anisotropy. The bound state energies up to J = 9 and the wave functions are calculated by analytically solving the Schrodinger equation based on the ab initio potential energy surface. The calculated fundamental frequencies of bending vibration and stretching vibration of the Kr-CNCN are 24.0 cm(-1) and 32.7 cm(-1), respectively. The transition frequencies and the spectroscopic constants of the Kr-CNCN system are predicted, and the relevant results are compared with the Kr-NCCN complex. The differences in the PES and bound state energy levels between the Kr-CNCN and Kr-NCCN complexes are clarified. These results will help to further explore the formation causes of CN radical in the interstellar medium and provide a theoretical basis for future experimental spectra research of the Kr-CNCN system.

Automated summary

The first ab initio potential energy surface of the Kr-CNCN system is investigated using the single double excitation coupled-cluster theory with noniterative treatment of triple excitation. The potential energy surface of the Kr-CNCN complex has a nearly T-shaped global minimum, and the interaction of the linear C-N-C-N-Kr geometry is stronger than that of the linear Kr-C-N-C-N structure. The calculated fundamental frequencies and spectroscopic constants are compared with the Kr-NCCN complex, and the differences in the potential energy surfaces and bound state energy levels are clarified. These results provide insights into the formation mechanism of CN radical and future experimental spectra research of the Kr-CNCN system.