A theoretical study of He_2ICI van der Waals cluster

摘要

The structure,energetics,and dynamics of He_2ICl complex in its ground state are studied by means of ab initio electronic structure and quantum-mechanical calculations.Interaction energies for selected He_2ICl configurations are calculated at the coupled-cluster [CCSD(T)] level of theory using a large-core pseudopotential for the I atom and the aug-cc-pVTZ and aug-cc-pV5Z basis sets for the Cl and He atoms,respectively.The surface is characterized around its lower five minima and the minimum energy pathways through them.The global minimum of the potential corresponds to a "police-nightstick (1)" configuration,the second one to a linear,the next one to tetrahedral configuration,and the following two to "bifork" and "police-nightstick (2)" structures,with well depths of-99.12,-97.42,-88.32,-85.84,and -78.54 cm~(-1),respectively.An analytical form based on the sum of the three-body parametrized HelCl interactions plus the He-He interaction is found to represent very well the tetra-atomic CSSD(T) results.The present potential expression is employed to perform variational five-dimensional quantum-mechanical calculations to study the vibrational bound states of the van der Waals He_2ICl complex.Results for total angular momentum j=0 provide the binding energy D_0 and the corresponding vibrationally averaged structure for different isomers of the cluster.Comparison of these results with recent experimental observations further justifies the potential used in this work.