CHEMISORPTION OF HYDROGEN ON STEPPED(410) SURFACES OF NI AND CU

The chemisorption of hydrogen on stepped (410) in step notation, (s)-[ 4(100)X(010)] surfaces of Ni and Cu has been studied using the embedde d-atom method (EAM). First, contours of the potential-energy surface ( PES) for atomic H on stepped (410) surfaces of Ni, Cu are presented an d compared with that of the flat (100) surfaces. It is found that step ped surfaces have more active adsorption sites and the binding energy of H is larger at the step sites. Then, the dissociation of the hydrog en molecule on the stepped (410) surfaces of Ni and Cu is also investi gated. The activation barrier E(a), adsorption heat q(ad) and correspo nding H-metal bond length R for different H-2, dissociation pathways a re calculated and the associated potential-energy surfaces are obtaine d. The calculated results show that in the process of H-2 approaching the concave site at the bottom of a step, the activation barrier for H -2 dissociation is lowest; while for H-2 approaching the outside edge of the terrace, the activation barrier is highest. Compared with that of H-2 on perfect (100) surfaces of Ni, Cu, the presence of steps can significantly lower the activation barrier for dissociation of H-2.