Helium dimer interaction energies from Gaussian geminal and orbital calculations

Nonrelativistic clamped nuclei interaction energies for a pair of helium atoms have been computed using the Gaussian geminal implementation of the coupled cluster theory with single and double excitations (CCSD). Effects of triple and quadruple excitations were subsequently included employing the conventional orbital approach and very large augmented, correlation-consistent bases extended by sets of bond functions. Up to the coupled cluster doubles (CCD) level, the Gaussian geminal expansions provide nearly an order of magnitude better accuracy than orbital expansions even if the latter results are extrapolated. The recommended values of the helium dimer interaction energy are 292.54 +/- 0.04 K, -11.009 +/- 0.008 K, and -4.619 +/- 0.007 K at the interatomic distances equal to 4.0, 5.6, and 7.0 bohr, respectively. The major contributions to the error estimates come from the orbital parts of the calculations beyond the CCSD level.