Theoretical Studies On The Weak Intermolecular Interactions Of Rg_n-N₂O(Rg=Kr,Xe;n=1,2) Systems

Theoretical studies on the vdW molecular ro-vibrational spectrum from abinitio potential energy surfaces (PESs) could predict and assign the energy levels,calculate the transition intensities, test the ab initio PESs, and provide usefulinformation about vdW molecular dynamics. A detailed understanding of theeffects of many-body nonadditive contributions in intermolecular interactions is ofconsiderable importance for the understanding of macroscopic systems. As Rg-N2Ois one of the most representative vdW systems, which shows a large angularanisotropy, it thus has become a challenging research field in recent years. In this work, we study the PESs and ro-vibrational spectrum of dimersKr-N2O and Xe-N2O, and the three-body nonadditive effects of trimers Kr2-N2Oand Xe2-N2O. For dimers Kr-N2O and Xe-N2O, ab initio PESs are generated usingsupermolecular approach at coupled-cluster (CCSD (T)) level, with an ECP basisset (Xe and Kr) and cc-pVQZ basis sets (N and O). including bond function. Twodimers have a T-shaped global minimum, where Rg atom is close to the O atom.With the ab initio PESs, we calculate the ro-vibrational energy levels usingSinc-DVR method. The CCSD (T) PES supports 62 and 97 vibrational bound statesfor Kr-N2O and Xe-N2O complexes respectively. We also calculated therovibrational levels of two dimers with N2O in its ground and ?3 excited states, andthe calculated rotational transition frequencies are in good agreement withexperimentally observed data. For trimers Kr2-N2O and Xe2-N2O, optimal molecular structures aredetermined by means of second-order M?ller-Plesset (MP2) method. Both trimersare found that the distorted tetrahedral structure (T-trimer) is the global minimum,and the planar structure (L-trimer) is the local minimum. Three-body nonadditiveeffects are performed using CCSD (T) method for both structures. Our calculationsshow that the nonadditivity is quite small percentage, and the nonadditive effectslead to the destabilization for both trimers.