Surface-diffusion mechanism versus electric field: Pt/Pt(001)

Ab initio calculations agree with field ion microscopy (FIM) that the barrier to substitutional diffusion of a Pt atom on Pt(001) varies linearly with external electric field. changing similar to0.1 eV per V/Angstrom and increasing for fields oriented to push electrons into the surface. But with a computed hopping barrier remaining >0.5 eV higher than that for substitution, they contradict the idea that a change in FIM site visitation at fields of 1.5-2 V/Angstrom and temperatures similar to 265-284 K can be attributed to the onset of hopping.