Ab Initio Study Of Spectroscopic Constants And Anharmonic Force Field For FClO₂/ClClO₂Molecules

Molecules containing halogen have aroused wide attention recently because of theirrole on atomospheric ozone damagement. The scientists began to study the structures andspectral properties of these molecules so that they can have a better understanding of themand monitor them in the atmosphere. The core of this dissertation is to employe high levelab initio calculations to study the equilibrium spectroscopic constants and the anharmonicforce field of FClO2and ClClO2, respectively. Submitting some spectroscopic constantsinto the corresponding energy level formula, one can obtain the computed rotational energyof molecule in the study, which is conducive to assign the observed rotational energy ofmolecules.Firstly, we calculate the equilibrium geometry structure of FClO2using B3LYP,B3PW91, B3P86with cc-pVQZ and6-311++G(3df,3pd); on the base of getting theequilibrium geometry, we calculate the spectroscopic constants and anharmonic force fieldof FClO2. In addition, we compared some spectroscopic constants, like the equilibriumgeometry structures, rotational constants on the ground state, harmonic and fundamentalfrequencies, quartic and sextic centrifugal distortion constants, coriolis coupled constants,with the relevant experimental and theoretical data. Besides, we predicted the otherconstants, such as the equilibrium rotational constants, anharmonic constants,vibration-rotational international constants, third-order and forth-order force constants. Theresults show that the B3P86results are in excellent agreement with experiment andrepresent a substantial improvement over the results obtained from B3LYP. The B3PW91method is also an advisable choice to study anharmonic force field of molecules. Theresults also show that with the same method, results using the basis set of6-311++G(3df,3pd) are closer to the experimental data than the results using the basis setof cc-pVQZ.Secondly, we calculated the equilibrium geometry structure and the anharmonic forcefield by the same level of theory for ClClO2. From the calculated results, we can see thatthe calculated values of B3P86method are perfectly agreement with the experimental data.Besides, predictions of some spectroscopic constants are expected to be useful for thefuture experimental work, while the B3LYP method can also reproduce the experimental data.