A density functional theory study on the adsorption of chlorobenzene on the Si(111)-7x7 surface

The adsorption of chlorobenzene (ClPh) on the Si(1 1 1)-7 x 7 surface has been investigated with the B3LYP density functional method. All possible adsorption configurations of chlorobenzene have been investigated. Binding energies including zero-point vibrational energy correction of different adsorption configurations were calculated at the B3LYP/6-31 G(d,p) level of theory. It was found that mono-sigma binding states are very instable. They will quickly transfer to the more stable di-sigma binding states. Upon heating, the di-sigma bonded chlorobenzene will desorb and then break its C-Cl bond to form a Si-Cl bond. Upon further heating, the desorbed chlorobenzene will break the C-H bond to form a Si-H bond. All four types of bindings prefer the unfaulted half of the unit cell and the center-rest atom adsorption sites. The most stable di-sigma binding state is a 2,5 binding configuration. The calculated binding energy for this configuration is 23.73 kcal mol(-1), in good agreement with the experimental desorption energy barrier of 23.30 kcal mol(-1).