Theoretical Study Of Potential Energy Surfaces And Ro-vibrational Spectra For Rg_n-N₂O

The study of potential energy surfaces(PESs) and ro-vibrational spectra for vdW systems Rgn-NiO, which is important for atmospheric chemistry, has become a challenging research field in recent years. Delicate theoretical studies can predict and assign the energy levels, provide useful information about vdW molecular dynamics, and reveal the nature of the intermolecular interactions.In this work, the PESs and ro-vibrational spectra of dimers Rg-N2O, the three-body nonadditive effects of trimers Rga-NiO, and conformations of clusters Rgn-N2O(n>2) have been investigated.For Ar-N2O, Ne-lSbO and He-NjO, ab initio PESs are generated using supermolecular approach at coupled-cluster(CCSD(T)) or fourth-order M011er-Plesset(MP4) level, with large basis sets including bond function. Three trimers have a T-shaped global minimum. From heavier Ar to lighter He, the PES is more and more flat and the intermolecular force is more and more weak. With the ab initio PESs, we calculate the ro-vibrational energy levels of three dimers and their isotopomers using Sinc-DVR method. The calculated rotational transition frequencies are in good agreement with experimental data.For Ar2-N2O and Ne2-N2O, their optimal molecular structures are determined using MP2 method. For both trimers, the distorted tetrahedral structures are found to be situated in the global minima, whereas the planar structures in the local minima. Three-body nonadditive effects are performed using CCSD(T) method. Our calculations show that the nonadditivity is quite small percentage, and the three-body effect of Ne2-N2O is weaker than that of Ar2-N2O.The global minima of Rgn-N2O(n>2) are found using powell method, with two-body potential model. Our calculations indicate that for Arn-N2O, the first five Ar atoms form the first solvation ring, and the first 17 Ar atoms complete the first solvation shell around N2O. But for Nen-NiO and Hen-N2O, the first six Ne or He atoms form the first solvation ring.