Origin of the reactivity on the nonterminated (100), (110), and (111) diamond surfaces: An electronic structure DFT study

The reactivity of nonterminated diamond low-index surfaces has been evaluated using density functional theory (DFT). The intrinsic electronic structures of the topmost carbon atoms of diamond (100)-1 x 1, (100)-2 x 1, (110)-1 x 1, (111)-1 x 1, and (111)-2 x 1 surfaces have been calculated and analyzed using highly accurate numerical basis set first-principle techniques. The following reactivity indicators have been utilized: Fukui functions, electrostatic potential, and Kohn-Sham orbitals (highest occupied and lowest unoccupied). Their spatial representations have been mapped onto a charge density isosurface whereby plausible reactive sites were identified and related. Specifically, the change in chemically reactivity induced by a I x I to 2 x I surface reconstruction has been discussed. In addition, density of states and the deformation density of the topmost carbon atoms have been included. Most often the sites of electrophilically susceptible areas correspond to the mapping of f(-) function, electrostatic potential, and highest occupied molecular orbital. Conversely, nucleciphilic sites correspond to the f(+)-function and the lowest unoccupied molecular orbital. However, some discrepancies are found, and it seems that the Fukui functions yield more accurate results due to orbital relaxation effects taken into account. The results herein were furthermore compared to adsorption Studies of H-, O-, and OH-terminated diamond (100) and (I 11) surfaces, respectively. It was concluded that the reactivity of diamond surfaces can be evaluated by using DFT techniques, which will thereby make it possible to increase the knowledge about thin film growth mechanisms, Surface functionalization, and reconstructions.