Modification of Cu-H bonding near a Ru(001)surface.

Surface Linearized Augmented Plane Wave (SLAPW) total energy calculations are used to study the 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(1x1)/Cu(1x1)/Ru(0001) vs, H(1x1)/Cu(111) roughly obey an "effective medium" picture: the H atoms prefer to reside at a particular clean-surface charge density (0.013 -0.015a. u.), and vibrate along the surface normal with a frequency omega subscript perpendicular proportional to the local, clean- surface normal charge density gradient. This results in a predicted 20% reduction of omega subscript perpendicular on Cu(1x1)Ru(0001) surface relative to omega subscript perpendicular for Cu(111).