Wrong bonds

The BF3 molecule is planar with bond angles of 120 . The 2p orbitals are perpendicular to each other, with angles between them of 90°. Thus, three atoms bound to three 2p orbitals would not form a planar structure and would have the wrong bond angles. If two F atoms bonded to two 2p orbitals on B and the third F bonded to the 2s orbital, the resulting... 

The cross-bonded terms cxCy/ ax and caCaFay result from interaction of X and Y with the wrong bonding hybrids on A. The magnitudes of these terms can usually be judged from simple overlap considerations. Unless X and Y are of quite dissimilar electronic character, the two cross-bonded terms are inherently of similar magnitude and therefore tend to cancel one another out. Thus, cross-bonded terms tend to make only minor contributions to geminal delocalization. 

What are the differences when we deal with internal surfaces i.e., interfaces) instead of free surfaces Although more complex in detail, wrong bonds are again responsible for internal surface Gibbs energies. Therefore, we normally expect cusps to occur in Eb vs. 0 (y vs. 0) plots (Fig. 3-9). 

FIGURE 3 Ball and stick model of the (1210) prismatic stacking fault in GaN. Each atom is fourfold coordinated and there are no wrong bonds [13]. 

Correcting inconsistencies, such as prescribing the wrong bond order between atoms in some molecules, as well as assigning ambiguous names in others ... 

For such binary compounds as GaAs there can be only a few wrong bonds (Ga-Ga or As-As), and in some idealized descriptions there are no wrong bonds and thus only even rings. 

Fig. 19.2 Pair correlation functions at 300 K for pure and doped Ge2Sb2Te5. Partial pair correlation functions for amorphous structures are on the left (a-e) and for crystalline structures are on the right (f-j). WB stands for wrong bonds...

Table 19.6 Computation of wrong bonds and the estimation of the ciysteillization time in doped and undoped Ge2Sl>2Te5...

Doptmt Wrong bonds in fraction Incubation period (ps) Crystallization period (ps) ToUil (ps)... 

Keeping these two types of structures in mind, we find from the literature that homopolar bonds like Ge-Ge or As-As are often considered defective or wrong bonds. Here we have to emphasize that such homopolar bonds by their nature are different from the defective bonds defined above, which involve localized electrons or holes. Therefore, in this chapter, we will use the term "homopolar bonds" rather than "wrong bonds" or "defective bonds" in order to emphasize the differences between them. Obviously, homopolar bonds are also a kind of "normal" bond structure. 

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