Energetics of hydrogen chemisorbed on Cu(110): A first principles calculations study

In the current study we present a potential energy surface(PES) for atomic hydrogen chemisorbed on Cu(110) at Theta =1/8 monolayer (ML) obtained from a plane-wave, gradient-corrected, density functional calculation. This PES is markedly different from and significantly more complex than that predict ed by empirical embedded atom method (EAM) calculations. Our results, for e xample, suggest strongly that the hollow (HL) site is not the preferred bin ding site for this system. In our calculations, both the short bridge (SB) and pseudo-threefold sites are energetically more favorable than the hollow (HL) site. Energetically, we find the SB site to be slightly lower (30 meV ) than the pseudo-threefold site. We also find, however, that the calculate d vibrational frequencies for the pseudo-threefold site agree more closely with experimental electron energy loss data than for the SB site. In view o f the relatively flat region between adjacent pseudo-threefold sites along the cross-channel [001] direction, we speculate that the hydrogen atom moti on at low coverages may be two-dimensional rather than quasi-one-dimensiona l in character. (C) 2000 American Institute of Physics. [S0021-9606(00)3064 0-7].