Abstract
Surface linearized augmented plane wave (SLAPW) total energy calculations are used to study differences between Cu-H bonding on Cu(111) and on a pseudomorphic Cu monolayer on a Ru(0001) substrate. Bond lengths and vibration frequencies for H(1×1)/Cu(1×1)/Ru(0001) versus H(1×1)/Cu(111) roughly obey an “effective medium” picture: the H atoms prefer to reside at a particular clean-surface charge density (0.013-0.015 au), and vibrate along the surface normal with a frequency, ω ⊥, proportional to the local, clean-surface normal charge density gradient. This results in a predicted 20% reduction of ω ⊥ on Cu(1×1)/Ru(0001) surface relative to ω ⊥ for Cu(111). At the same time, the weakening of the Cu-Cu bond when a Cu(111) layer is strained to fit pseudomorphically on Ru(0001) is partially compensated by the fact that the Cu-Ru bonding is stronger than Cu-Cu. Thus the binding energy of a H monolayer on Cu(1×1)/Ru(0001) is calculated to be only 0.05 eV/H greater than on Cu(111).
Published Version
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