Competing Reconstruction Mechanisms in H/Ni(110)
The mechanisms of the hydrogen-induced reconstructions of Ni(110) have been investigated. Below ~180 K a (2 × 1) lattice gas structure with өH=1.0 transforms into a 2D-(1 × 2) structure during addition of hydrogen up to өH =1.5. The phase transition, which involves a reconstruction of the surface, exhibits first-order behavior with no apparent activation energy. In contrast, at T >180 K and already at low coverages, an activated, local transformation into a more stable ID structure (’streaked structure’) occurs. A lattice distortion to optimize the local metal structure with respect to the metal-ad-sorbate bond and thus increase the binding energy is introduced as a general model for many such adsorbate-induced surface phase transformations.
KeywordsEnthalpy Hexagonal Nism Chemisorption Supersaturation
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