Geometries and Bond Energies of the He-MX, Ne-MX, and Ar-MX (M = Cu, Ag, Au; X = F, Cl) Complexes

Calculations on the He center dot center dot center dot MX, Ne center dot center dot center dot MX, and Ar center dot center dot center dot MX (M = Cu, Ag, Au; X = F, Cl) complexes at the CCSD and CCSD(T) levels of theory have been carried Out. The geometries of the Ar-MF complexes are in good agreement to those determined via microwave spectroscopy. The RG center dot center dot center dot MX (RG = He, Ne, and Ar) dissociation energies for these complexes have been evaluated by extrapolation to the complete basis set limit. The importance of the inclusion of diffuse functions to the determined dissociation energies of these complexes are discussed with comparison to recent work. For the He center dot center dot center dot CuF and He center dot center dot center dot AuF complexes, the dissociation energies have been found to be significant, at approximate to 26 kJ mol(-1), while the bonding in the chlorine analogous is only approximate to 15 kJ mol(-1). The bonding between the helium and the metal atoms in the He center dot center dot center dot CuF and He center dot center dot center dot AuF complexes has been investigated by using an atoms-in-molecules (AIM) analysis to-ether with an evaluation of the dipole/induced-dipole and ion/induced-dipole interactions. This analysis has shown that the bonding in these complexes is slightly covalent in nature. For the He center dot center dot center dot AgF and Ne center dot center dot center dot MF (M = Cu, Ago, Au) complexes the dissociation energy is much smaller and the AIM analysis shows the bonding is more electrostatic in nature. Calculations have also been carried out on He center dot center dot center dot AgCl and Ne center dot center dot center dot MCl (M = Cu, Ag, Au) complexes for the first time in addition to the Ar center dot center dot center dot MX (M = Cu, Ag, Au X = F, Cl) complexes. The RG center dot center dot center dot MCl complexes are found to be more weakly bound than the corresponding RG center dot center dot center dot MF complexes as a result of the difference in electronegativity of the halogen. For each complex, bond lengths, rotational constants, and harmonic vibrational frequencies have also been evaluated.