Accurate intermolecular ground-state potential-energy surfaces of the HCCH-He, Ne, and Ar van der Waals complexes.

Accurate ground-state intermolecular potential-energy surfaces are obtained for the HCCH-He, Ne, and Ar van der Waals complexes. The interaction energies are calculated at the coupled cluster singles and doubles including connected triple excitations level and fitted to analytic functions. For the three complexes we start with systematic basis set studies carried out at several intermolecular geometries, and using augmented correlation consistent polarized valence basis sets x-aug-cc-pVXZ (x=-,d; X=D,T,Q,5), also extended with a set of 3s3p2d1f1g midbond functions. The aug-cc-pVQZ-33211 surfaces of HCCH-He, Ne, and Ar complexes are characterized by absolute minima of -24.22, -50.20, and -122.17 cm(-1) at distances R between the rare-gas atom and the HCCH centers of mass of 4.35, 3.95, and 3.99 A, respectively; and at angles between the vector R and the HCCH main symmetry axis of 0 degrees , 43.3 degrees , and 60.6 degrees . The results are compared and considerably improve those previously available.