The importance of memory effects in Arrhenius surface diffusion barrie
rs E-A is studied within the lattice-gas model. It is found that E-A o
f tracer diffusion is strongly affected by memory effects at finite co
verages and low temperatures, where about 10-50% of E-A arises from te
mperature variations in the memory effects. In the Arrhenius barrier o
f collective diffusion, the memory contribution is also significant bu
t less pronounced than in tracer diffusion. Interpretation of E-A's in
terms of microscopic activation processes is further discussed. (C) 1
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