The rates of Br atom diffusion on several single crystalline Cu surfaces were investigated. Density functional theory was used to study the diffusion of isolated Br atoms on a flat Cu surface, Cu(111), two Cu surfaces with straight steps, Cu(221) and Cu(533), and two kinked Cu surfaces, Cu(643) and Cu(531). The Br diffusion was rapid on the flat Cu(111) surface with a barrier of ΔEdiff = 0.06eV and a hopping frequency of ν = 4.8 x 1010/s at 150K. On the stepped and kinked surfaces the effective diffusion barriers lay in the range ΔEdiff = 0.18–0.31eV. Thus the rates of diffusion were many orders of magnitude slower on stepped and kinked Cu surfaces than on the Cu(111) surface. Nonetheless, at temperatures relevant for alkyl bromide debromination on Cu surfaces, Br atoms remained sufficiently mobile that they could explore all available binding sites on the timescale of the debromination reaction.

Bromine Atom Diffusion on Stepped and Kinked Copper Surfaces. D.M.Rampulla, A.J.Gellman, D.S.Sholl: Surface Science, 2006, 600[10], 2171-7