Consistent picture for the wetting structure of water/Ru(0001)

The wetting layer of D2O on Ru(0001) has been reanalyzed with ab-initio molecular dynamics and full-potential calculation. Comparison of vibrational spectra and work function with experiments favors the picture of molecular wetting rather than partial dissociation. A mixture structure consisting of both hydrogen-up and hydrogen-down bilayers is found to be consistent with experiments. The barrier and minimum energy path for bilayer dissociation have been determined. The dissociation barrier is larger than that for desorption, suggesting that dissociation is kinetically forbidden at low temperatures. These finding resolve the current controversy between previous calculations and experimental observations.