Three-Dimensional ab Initio Potential and Ground State Dynamics of the HeI2 Complex
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Abstract
The interaction potential for the HeI2 molecule is studied using the coupled-cluster (CCSD(T)) method. A correlation-consistent triple-ζ valence basis set in conjunction with a large-core Stuttgart−Dresden−Bonn (SDB) relativistic pseudopotential is used for the iodine atoms, whereas augmented correlation-consistent basis sets, aug-cc-pV5Z, are used for the He atom, supplemented with a set of bond functions. The potential energy surface of the ground electronic state of HeI2 shows a double-minimum topology, with an isomerization barrier of 25.64 cm-1. Bound state calculations are carried out for J = 0, and the lowest vibrational vdW level corresponds to the linear configuration, while a level found only 0.7 cm-1 above is assigned to a T-shaped isomer. The CCSD(T) dissociation energies for the linear and T-shaped configurations are found to be = 15.38 cm-1 and = 14.68 cm-1, with vibrationally averaged structures of R0 = 5.34 and 4.40 Å, respectively. The above results are in good accord with experimental investigations available for the T-shaped isomer. Further, the present calculations predict the existence of a linear isomer, and the rather small energy difference between them indicates that linear and T-shaped isomers can coexist even at low temperatures for the He−I2 complex.
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