Bond-charge increment

Variations, including the atom-atom charge transfer (AACT) " and the bond-charge increment model, only allow for charge to flow... 

Consensus Bond-Charge Increments Fitted to Electrostatic Potential or Field of Many Compounds Application to MMFF94 Training Set. 

It is often assumed that the correlation corrections to the SCF atomic and molecular energies, which are an order of magnitude lower than the relaxation energies, approximately cancel out in Eqn (2). However, as we shall see, this is not true for the relaxation corrections. If one uses, for the terms in brackets, quadratic functions of the charge increment on the bonded atom similar to the fits shown in Fig. 4, one obtains, for the relaxed and Koopmans ionization-energy shifts ... 

In contrast to the point charge model, which needs atom-centered charges from an external source (because of the geometry dependence of the charge distribution they cannot be parameterized and are often pre-calculated by quantum mechanics), the relatively few different bond dipoles are parameterized. An elegant way to calculate charges is by the use of so-called bond increments (Eq. (26)), which are defined as the charge contribution of each atom j bound to atom i. 

Table 4.32. Average bond lengths ptF, incremental F binding energies A E(+F ), and platinum atomic charge Qnfor PtF (6 ")+ complexes (see Fig. 4.49)...

Table 5.20. Cooperative (n-dependent) properties of linear formamide chains (see Figs. 5.19 and 5.27), showing the incremental binding energy AEn, average H-bonded Ron and Rmi distances, and partial charges Q and Qn on terminal monomers of the (H2NCHO) chain (for comparison, the cyclic pentamer in Fig. 5.27(c) has Ro u = 1.879 A, Rm = 1-024 A, and average H-bond energy 7.92 heal mol x)...

Figure 10.7 During the adsorption of molecular nitrogen onto iron metal, the two nitrogen atoms donate an increment of charge to adjacent atoms of iron on the metal surface, as depicted by the vertical arrows. The N=N triple bond cleaves partially, with a resultant bond order of about 1.5...

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