Coverage-dependent diffusion of CO on Ni(100)

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Abstract
The coverage dependent diffusion rate of CO on Ni(100) has been studied by laser‐induced desorption methods. The CO diffusion rate varies with the morphology of the adlayer. At low coverages, where the CO is disordered, the rate is relatively low but constant. At high coverages where a c(5√2×√2)R45 structure is known to prevail, the rate is significantly faster but again constant with coverage. Between these two regions (0.3<θCO c(2×2) structure develops, the rate is intermediate and tends to increase with coverage. The activation energy Ed decreases but the preexponential term D0 also decreases when the rate increases. This compensation effect between Ed and D0 is used to anticipate surface phase changes.