High-accuracy Potential Energy Surface And Full Quantum Calculation Rovibrational Spectra For H₂O-N₂ And D₂O-N₂ Complexes

For a long time,spectral detection is one of the important means for scientists to characterize the structure and properties of materials.Through the study of spectra,people can obtain a lot of information such as the equilibrium configuration and reaction kinetics of molecules.Among them,microwave and infrared spectroscopy can provide information of molecular rotation and vibration,so they are used as the important means of qualitative and quantitative analysis of molecular and complex structures.With the development of technology and the improvement of the performance of experimental equipment,most of the experimental spectral measurements are mainly aimed at small molecules,weak interaction systems or clusters.Therefore,how to accurately analyze a large number of experimental spectral data is a difficult problem for experimenters.The development of theory and experiment are complementary,and the development of experiment can not be separated from the guidance of theory.With the improvement of computer performance,the theoretical study of weak interaction between molecules has reached a new height.The study of the vibrational spectra of the van der Waals system with large amplitude motion is not only an opportunity,but also a challenge.A deep understanding of the energy balance of solar energy absorption and earth radiation is the key to revealing the"greenhouse effect",global temperature and climate change.Theoretical and experimental studies on the infrared absorption spectra of van der Waals complex formed by water and other atmospheric molecules play an important role in the analysis of solar energy absorption in the infrared band.Nitrogen is the most important component in the atmosphere,so water and nitrogen complex?H₂O-N₂?is the most important system.The main research contents of this project are as follows:A six-dimensional?6D?ab initio potential energy surface?PES?for the van der Waals complex of H₂O-N₂ which explicitly incorporates the intramolecular Q₂ bending normal mode of the H₂O monomer is presented.The electronic structure computations have been carried out at the explicitly correlated coupled cluster theory[CCSD?T?-F12]with an augmented correlation-consistent triple zeta basis set and an additional bond function.Analytic five-dimensional?5D?intermolecular PESs for v₂?H₂ O??28?0 and 1are obtained by fitting to the multi-dimensional Morse/Long-Range potential function form.These fits to 40890 points have the root-mean-square discrepancy of 0.88 cm^-1for interaction energies less than 2000.0 cm^-1.The resulting vibrationally averaged PESs provide good representations of the experimental microwave and infrared data:?a?for microwave transitions of H₂O-N₂,the root-mean-square discrepancy?RMSD?is only 0.0003 cm^-1.?b?The calculated infrared band origin shifts associated with the ₂v bending vibration of water are 2.210 and 1.323 cm^-1 for H₂O-N₂ and D₂O-N₂,in good agreement with the experimental values of 2.254 and 1.266 cm^-1.?c?For A₁ symmetry of H₂O-N₂ complex,the predicted infrared transition frequencies make in good agreement with the experiment and the RMSD is only 0.001 cm^-1.The precision and reliability of the potential energy surface are ensured by the strict detection of the spectral properties such as microwave,infrared,vibration frequency displacement,etc.,which lays an important foundation for further study of the spectrum and energy transfer process of H₂O in N₂ cluster or matrix,and analysis of the absorption of solar energy in microwave and infrared band.