Valence-shell electron-pair repulsion application

Once computed on a 3D grid from a given ab initio wave function, the ELF function can be partitioned into an intuitive chemical scheme [30], Indeed, core regions, denoted C(X), can be determined for any atom, as well as valence regions associated to lone pairs, denoted V(X), and to chemical bonds (V(X,Y)). These ELF regions, the so-called basins (denoted 2), match closely the domains of Gillespie s VSEPR (Valence Shell Electron Pair Repulsion) model. Details about the ELF function and its applications can be found in a recent review paper [31],... 

The applications of valence bond theory, the valence shell electron pair repulsion theory, to the bonding and bond angles of triatomic molecules... 

The bonding in ground state PHg was also described in the framework of a generalized valence bond (GVB) theory [17]. A VB method, which was combined with the method of atoms in molecules [18], yielded a small d contribution (4%) in the P valence state [19]. For an application of the valence shell electron pair repulsion (VSEPR) theory, see [20]. 

Electron density maps based on theoretical calculations (methods in parentheses) are given in [22] (SCF-MO [23] also for the highest occupied MO 5ai), in [24] (SCF and Cl also for the three valence orbitals), in [10] (SCF-Xa-SW for the valence orbitals and the total valence shell), in [25] (SCF and SCGF [self-consistent group function]), and in [26] (united atom). The Laplacian V p of the charge density p showed four local concentrations of electronic charge in the valence shell of the central P atom in accordance with the VSEPR (valence shell electron pair repulsion) model [27] for this latter model and its application to PH3, see [28 to 31]. 

In Appendix 2 is outlined the most popular and successful simple model for predicting molecular geometry of main group compounds, the valence shell electron pair repulsion (VSEPR) model. However, alongside it are presented the results of some detailed calculations which prompt the comment the VSEPR model usually makes correct predictions, but there is no simple reason why . The problem of the bonding in transition metal complexes will be the subject of models presented in Chapters 6, 7 and 10 this last chapter reviews the current situation. At this point it is sufficient to comment that the most useful applications of current simple theory are those that start with the observed structure and work from there. In the opinion of the author, the general answer to the question posed at the head of this section is that we really do not know. 

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