DFT study of self-coupling reaction of CF 2(ads) coadsorbed on Cu(111) surface for forming CF2=CF 2(g)

Abstract

Total energy calculations based on the density functional theory (DFT) with ultrasoft pseudopotential, generalized gradient spin-polarized approximation and the partial structural constraint path minimization (PSCPM) method were carried out to establish the energetically more favorable reaction pathways for the self-coupling reaction of coadsorbed CF 2(ads) leading to the formation of CF 2=CF 2(ads) on the Cu(111) surface. In addition, the calculated electronic properties, namely partial density of states (PDOS), suggest that the initial breaking of the Cu(111)–CF 2(ads) bond associating with the electron delocalization on the Cu(111) surface and the electron transfer from Cu(111) to both units of CF 2(ads) are factors controlling the energy barrier for self-coupling reaction. Finally, the calculated energy barrier (0.310 eV) for the self-coupling reaction of CF 2(ads) coadsorbed on the Cu(111) surface in comparison with that (0.204 eV) for the single α-fluoride elimination of adsorbed CF 3(ads) on the Cu(111) surface qualitatively manifests that the formation of CF 2 = CF 2(g) at 250 K is limited by the self-coupling reaction of coadsorbed CF 2(ads) instead of the single α-fluoride elimination of adsorbed CF 3(ads).