The van der Waals potential energy surfaces and structures of He–ICl and Ne–ICl clusters

The potential energy surfaces of the ground electronic state of rare gas interhalogen van der Waals molecules, Rg–ICl ~Rg5He, Ne!, are calculated at CCSD~T! ~coupled cluster using single and double excitations with a noniterative perturbation treatment of triple excitations! level of theory. Calculations have been performed with specific augmented correlation consistent basis sets for the noble atom ~Rg!, supplemented with an additional set of bond functions. For iodine atom a correlation consistent triple zeta valence basis set in conjunction with large-core Stuttgart– Dresden–Bonn relativistic pseudopotential has been employed. The CCSD~T! results predict the existence of three minima on the Rg–ICl potential energy surfaces at collinear ~Rg–ICl!, antilinear ~Rg–ClI!, and near T-shaped configurations, with the collinear structure to be the lowest one. Bound states calculated from the intermolecular potential surfaces show that zero-order vibrational corrections do not alter the stability of the three structures. Equilibrium intermolecular distances, binding energies, and isomerization barriers are evaluated using the CCSD~T! potentials and compared with previous theoretical and/or experimental results. © 2002 American Institute of Physics. @DOI: 10.1063/1.1506920#