Ground state potential energy curves for He-2, Ne-2, Ar-2, He-Ne, He-Ar, and Ne-Ar: A coupled-cluster study

Potential energy curves for three homonuclear (He-2, Ne-2, Ar-2) and three heteronuclear (He-Ne, He-Ar, Ne-Ar) rare gas dimers are presented. The curv es were calculated using several correlation consistent basis sets and the supermolecule single and double excitation coupled-cluster theory with noni terative perturbational treatment of triple excitations, CCSD(T). The most accurate results were obtained with the aug-cc-pV5Z basis set supplemented with an additional (3s3p2d2f1g) set of bond functions. The results obtained with a smaller aug-cc-pVQZ+(3s3p2d2f1g) basis set are almost as accurate. Both basis sets give results in better agreement with potentials based on e xperiments than the recent results obtained with larger d-aug-cc-pV6Z and t -aug-cc-pV6Z basis sets but without bond functions. For each complex and ea ch basis set a fitted potential energy curve is given. In addition, for eac h complex, with the exception of He-2, the values of R-e, D-e, B-0, D-0, an d < R >(0) are given. For He-2 no bound states were found so only the value s of R-e and D-e are presented. For Ne-2, Ar-2, and Ne-Ar the calculated fr equencies of vibrational and pure rotational transitions are shown to be in good agreement with the experimental results. (C) 1999 American Institute of Physics. [S0021-9606(99)30547-X].