THEORY OF THE D(10)-D(10) CLOSED-SHELL ATTRACTION .1. DIMERS NEAR-EQUILIBRIUM

We study the dependence of the aurophilic attraction (Au-1-Au-1) in pe rpendicular model systems of the type [(ClAuPH3)(2)] on the ab initio method, basis set and different pseudopotentials used, and on relativi ty. The effects of varying the ''halogen'' (X = F, H, Cl, Me, Br, -C=C H, I), the ''phosphine'' (L = PH3, PMe3-N=CH) and the metal (M = Cu, A g, Au) on the M-M' interaction of the [(XML)(2)] dimer are also studie d. The depth of the interaction potential increases with the softness of the group X. It decreases by 27% for M = Au, X = Cl and L = PH3 if relativistic effects are omitted at fixed geometry.