Calibration of chemical bonding between benzenedithiolate and gold: the effects of geometry and size of gold clusters

The effects of geometry and size of gold clusters on the chemical bonding between benzenedithiolate (BDT) molecule and gold clusters have been evaluated for several different BDT-nAu complexes. The original potentials were developed based on BDT-1, 2 Au complexes (Leng et al., J. Chem. Phys. 122(24), 244721 (2005)). Density functional theory (DFT) calculations are employed to calibrate the bond-stretching behaviour between BDT and gold atoms. It has been found that, to some extent, the shape of bonding curves depends on the gold cluster geometry and size. This is particularly obvious for the on-top bonding case. However this effect does not alter molecular packing structure on Au (111) surface and has only a minor effect on local bonding geometry. The Mulliken charge distribution at the bonding interface (i.e. among bonded atoms) also does not show any impact on the global packing structure. The pure chemical bonding, which was derived from the total DFT energy subtracting the non-bonded terms, dominates the local bonding behaviour between BDT molecules and Au clusters.