Surfaces rehybridization

A set of simple physical and chemical principles can be used to understand and predict the surface reconstruction or faceting, which occurs on oxide surfaces.8,9 These include (1) autocompensation of stable surfaces, (2) rehybridization of the dangling bond charge density, (3) formation of an insulating surface, (4) conservation of near-neighbor bond lengths (which minimize the formation of surface strain fields), and (5) surface kinetic factors. We shall briefly discuss all of these factors governing the surface reconstruction of metal oxide. 

Once a particular surface structure has been determined to be stable (i.e., autocompensated), the primary factor determining the nature of the surface reconstruction is the energy that can be gained by rehybridizing the surface dangling bond charge density in response to the reduced coordination at the surface. As a consequence, a charge transfer between the atoms at the surface takes place and this results in the formation of new bonds between surface atoms adsorbed to the surface (also known as adatoms). The formation of new bonds on the surface leads to different chemical and physical properties at the surface.11... 

Table 13.5 lists the ABads values obtained. On the basis of these calculations, the phenyl isocyanide should adsorb on the on-top sites on Ag and in the three-fold hollow sites on Au. On Au, phenyl isocyanide was calculated to adsorb on the three-fold hollow site with a slight rehybridization of the N atom, which causes a slight hit (27 °) from the surface normal. However, the energy difference between the most stable structure and the one with a linear C=N-C unit is only 0.3 kcalmoT. ... 

The conjugated C-atoms of a fullerene respond to the deviation from planarity by rehybridization of the sp o and the p Jt orbitals, since pure p character of Jt orbitals is only possible in strictly planar situations ]56]. The electronic struchue of non-planar organic molecules has been analyzed by Haddon using the Jt orbital axis vector (POAV) analysis. For Cjq an average o bond hybridization of sp and a fractional s character of 0.085 (POAVl) or 0.081 (POAV2) was foimd ]59-63]. Consequently, the Jt orbitals extend further beyond the outer surface than into the interior of Cgg. This consideration implies, moreover, that fullerenes and, in particular, Cgg are fairly electronegative molecules [64, 65] since, due to the rehybridization, low-lying Jt orbitals also exhibit considerable s character. 

Even in the absence of a free electron gas that causes charge redistribution at low coordination number sites on metal surfaces there are strong chemical effects associated with atoms in surface irregularities. The rehybridization of localized electron orbitals should have a marked effect on the chemical... 

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