Group orbital density of states

The value to be used for n as a function of coordination number follows from Ek s.(2.212). is the Green s function of the undisturbed surface. The group orbital LDOS pf (n, E) for threefold and twofold symmetric as well as atop and twofold asymmetric coordination of a Bethe lattice simulating the (111) surface of a face-centered cubic lattice are sketched in Fig.(2.47). As expected the maximum of the group orbital density of states shifts to higher energy values if the coordination decreases. In the next section and in section 2.8, group orbitals arc shown to... 

Ek]uation (2.245) relates the chemisorption energy to the group orbital density of states at the Fermi level in similar fashion to Eq.(2.237b). Equation (2.248) is often satisfied for the occupied molecular orbital levels as well as unoccupied molecular orbitals of an adsorbate with respect to the d-valence electron levels of the surface. Its use is limited, because the interaction with the d-valence electrons is better described in the quasi-surface molecule limit. We will return to this later. In the second-order perturbation theory expression, one ignores the repulsive interaction of two orbitals that are doubly occupied (see also section 2.2.7). 

Figure 3.43a. Symmetric group orbital density of states as a function of the degree of delocalization.

Figure 3.60. Group orbital densities of state of the Ag (lU) face (...) atomic...

Figure 10.14 Partial density of states (PDOS) and group orbital densities of states (GODOS) for surface Ag 5s orbitals in bare Ag(lll) slab according to the extended Hiickel method. The dark solid line is the total Ag 5s PDOS. The Ag 5s GODOS are...

Figure 3.12. Group orbital Density of States as computed using Extended Hiickel theory for the s atomic orbitals of the Ag(l 11) surface ). The metal electron energy increases from right to left.

The group orbital is the combination of metal states coupling directly to the adsorbate state, and it is therefore the projection of the substrate density of states onto this... 

The group-orbital projected metal density of states, nd(e). can be characterized by its moments ... 

As described in the previous chapters, the bottom of the conduction band of metal oxides of group 12-14 elements is composed of empty M-s orbitals. The density of state features as observed by ELNES is therefore determined by the M-M interactions. An example of the effect of the M-M interaction on the... 

In the limit of ideal weak chemisorption, the chemisorption energy is proportional to the number of surface metal atom orbitals to which the adsorbate is coordinated, the interaction energy squared and two functions pi (n, Ep)y the corresponding surface group orbital local density of states at the Fermi level and a function that depends... 

Figure 2.66. Interaction of ba and 2r orbitals of CO with d, and d subband of (111) face of f.c.c. metal (Pt). Comparison between atop and threefold coordinaiiont l GO-LDOS = group orbital local density of states.

How CO will coordinate depends on the balance of the 5a interaction that prefers atop coordination and 2x interaction that prefers bridge coordination. Clearly a high workfunction metal favors 5a donation and hence atop coordination, whereas a low-workfunction metal favors 2x backdonation, which pushes the molecule to bridge coordination. Within the Bethc lattice approximation, which smoothes the valence electron band fine structure, the trends for the chemisorption energies are completely parallel to the trends in local density of states at the Fermi level of the corresponding group orbitals. 

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