کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5425838 | 1395867 | 2006 | 7 صفحه PDF | دانلود رایگان |
The rates of Br atom diffusion on several single crystalline Cu surfaces have been studied because of the potential impact of Br diffusion on the selectivity of alkyl bromide surface chemistry on Cu. Density functional theory (DFT) has been used to study the diffusion of isolated bromine atoms on a flat Cu surface, Cu(1 1 1), two Cu surfaces with straight steps, Cu(2 2 1) and Cu(5 3 3), and two kinked Cu surfaces, Cu(6 4 3) and Cu(5 3 1). Bromine diffusion is rapid on the flat Cu(1 1 1) surface with a barrier of ÎEdiff = 0.06 eV and a hopping frequency of ν = 4.8 Ã 1010 sâ1 at 150 K. On the stepped and kinked surfaces the effective diffusion barriers lie in the range ÎEdiff = 0.18-0.31 eV. Thus the rates of diffusion are many orders of magnitude slower on stepped and kinked Cu surfaces than on the Cu(1 1 1) surface. Nonetheless, at temperatures relevant for alkyl bromide debromination on Cu surfaces, bromine atoms remain sufficiently mobile that they can explore all available binding sites on the timescale of the debromination reaction.
Journal: Surface Science - Volume 600, Issue 10, 15 May 2006, Pages 2171-2177