A theoretical characterization of multiple isomers of the He2I2 complex

Graphical abstract: Minimum energy path as a function of angle for planar (a) and non-planar (b) configurations. The probability distributions for the five lowest vibrational vdW states of He2I2 are also depicted. Highlights: ► The work presented here is the most detailed description on intermolecular interactions and model structures for the He2I2 cluster. ► The results obtained from high level ab initio calculations and exact quantum calculations. ► Comparison with available experimental data from similar He2-dihalogen complexes provides information on intermolecular forces. ► These findings contributes to evaluate our approaches for extending them to larger systems. ► Accurate PESs for small molecules interacting with He atoms are in demand for studying superfluidity in He nanodroplets. - Abstract: The present work has been directed at studying the structures and stabilization energetics of different conformers of the ground state He2I2 cluster. The full interaction between I2 molecule and the He atoms is obtained from a sum-of-potentials scheme, using an analytical He–I2 potential parametrized to ab initio calculations plus the He–He interaction. Quantum mechanical variational calculations are carried out, and binding energies as well as radial/angular probability density distributions are computed for the lower-lying vibrational van der Waals states. We found that they correspond to three different structural models, namely tetrahedral, linear and 'police-nightstick'. Comparison of these results with recent experimental data available from high-resolution spectroscopy for similar tetraatomic He2-dihalogen complexes, contributes to evaluate their relative stability, and provides information about the importance of the multiple minima (global and local) of the potential surface used.