First-principles calculations of H adsorption on Pd(211) were performed by using density-functional theory within the generalized gradient approximation. It was found that the most preferred site was the three-fold hollow site on the terrace of Pd(211), with an adsorption energy of 0.52eV. The hexagonal close-packed and face-centred cubic sites were almost equally favourable, energetically. For sub-surface H adsorption on Pd(211) the octahedral site, with an adsorption energy of 0.19eV, was slightly more favourable than was the tetrahedral site (0.18eV). The calculated activation energy barrier, to H diffusing from the preferred surface site to the sub-surface one on Pd(211), was 0.33eV. This was compared with the 0.41eV on Pd(111). That is, there was an increase in the probability of finding sub-surface H in Pd(211). It was found that the diffusion barrier for H on the terraces of Pd(211) was 0.11eV, while that along the step-edge was only 0.05eV and that within the second layer (sub-surface) was 0.15eV.

Adsorption and Diffusion of Hydrogen on Pd(211) and Pd(111) - Results from First-Principles Electronic Structure Calculations. S.Hong, T.S.Rahman: Physical Review B, 2007, 75[15], 155405 (10pp)