In stark contrast to both the gas-phase and continuum solvation calculations, our "benchmark" QM/MM calculations show that the perpendicular adsorption mode generally becomes more stable than the parallel mode (see Fig. ). The only exception is for Pd (111), where strong chemisorption is involved, presumably overwhelming the influence of solvation. For parallel adsorption, we observed a much higher reduction in adsorption free energy, arising from competitive water adsorption (Fig. ): the number of remaining specifically adsorbed water molecules are far fewer in the case of parallel adsorption (Table ), as these water molecules are driven off the surface by the adsorption of the organic. In contrast, for the perpendicular mode, only one water molecule is displaced. As such, the net effect is to relatively favor the perpendicular mode, since this mode pays a far smaller "cost" to desorb the surface-bound water molecules.