Theoretical Studies On The Geometries Of Methyl Iodide Clusters

It is important to know the structures, stability and vibrationalspectra of molecule clusters in order to comprehend the formingmechanism, proton transfer process, solvation effect. And, it is alsohelpful for understanding the mechanics of chemical reaction.The stable structures and vibrational spectra of methyl iodidemolecule clusters are calculated using the density functional theorymethod. The calculated results show that for neutral methyl iodidemolecule clusters, from n=3 the cubic geometry is the most stablegeometry in the same size clusters. The stability of cubic geometrystructure is increasing with the growth of cluster size. The stablestructure of n=2 and the cubic geometry may be considered as the basiselement when larger structure cluster size are designed.For neutral methyl iodide clusters we also calculate their IRvibrational spectra and only assign CH3 stretching vibrational peak witha and b vibrational model. The calculated results show that thefrequencies associated with CH3 stretch decrease (red shift)with avibrational model and increase with b vibrational model. But all thesemodels shift to the peaks when methyl iodide in liquid. And from thisrule, we can see that with the growth of cluster size, some characters ofcluster would shift to corresponding characters when it becomes liquidor solid.