Core basin

Tables Nomenclature of valence basins. The expression in parenthesis corresponds to the list of core basins sharing a common boundary with the valence basin under scrutiny...

For the Electron Localisation Function (ELF) analyses, we have used the 6-311G basis set with the PW functional to be able to include the core basins in the representation. 

The molecular space is divided into core and valence basins, the latter being classified according to their connectivity to the core basins as monosynaptic basins, associated with electron pairs, or dissynaptic basins, associated with covalent bonds. Moreover, an integration of the electronic population over each basin gives the number of electrons in each of them and the fluctuation between basins is related to the electronic delocalisation [39]. 

Figure 5. Tridimensional visualisation of the ELF function for TiH3+ for the D3h and C3V symmetry, The ML3 topology of the C3v species is clearly seen in the side view. The orientation of the core basins vs. the Ti-H dissynaptic basins appears in the top view.

As in the case of phenol or monosubstituted benzenes12, ANI exhibits six C(C) and one C(N) core basins, six V(C,C), five V(C,H), one V(C,N), two V(N,H) and one V(N, lone pair) localization domains. Integration of the density over each domain allows the amount of electrons present there to be determined. Thus the C—C bonds are nearly equivalent and each V(C,C) basin classically contains about 2.7-2.9 electrons (close to 3.0), whereas the V(N) and V(C,N) basins have 1.8 and 1.9 electrons, respectively (Figure 5). Relative to benzene, an increase in the population of the V(Cor//1<>—Cm< M) basin is noticeable (0.1 e) whereas the populations of other domains remain almost unchanged. Overall, the above analysis is in line with the classical picture that chemists always have about the electron distribution in aniline. 

Fig. 9 Electronic localization function (ELF) for benzene. Left. ELF = 0.85 iso-surface. Right. ELF = 0.66 iso-surfaces. The right iso-surface is cut on the front side for showing the complex topology the Carbon core basins sharply separate from the scalar ELF field. The aromatic ELF basin is clearly defined. Both in the high or lower ELF value iso-surface, no separation between Sigma and Pi basins can be found, which is a characteristic of delocalized bonds, similar to that shown in Fig. 11. All the molecular plots reporting ELF iso-surfaces or MPD are performed using the Xcrysden program [44]...

There are basically two types of basins. On the one hand are core basins organized around nuclei (with Z > 2) and on the other are valence basins in the remaining space. The structure provided by the core basins closely matches the inner atomic shell structure. A valence basin is characterized by its synaptic order which is the number of cores to which it is connected [36]. To be connected to a core a valence basin must fulfill the three following conditions ... 

In principle, a core is always totally encapsulated by at least one valence basin and therefore propositions i) and ii) are redundant when / tends to zero unless the valence localization domains and a core domain have already merged into a single domian. In our description of the chemical bond a basin which contains a proton is considered as a valence basin except for the peculiar case of the very strong hydrogen bond for which a pseudo core shell is found around the bridging proton. The valence basins are therefore divided into mono-, di- and polysynaptic ones. As an example, a C-H bond is characterized by a disynaptic basin which encompasses the proton and shares a common separatrix with the carbon core basin. The nomenclature adopted to label core and valence attractors and basins is given in table 1. The attractors and basins are labeled as T[,](atom labels). T denotes... 

The analysis of ELF yields a partition into core and valence basins which correspond to the qualitative electron pair domains of the VSEPR model and have the same geometry as the VSEPR domains [72]. The core basins, labeled as C(A) where A is the atomic symbol of the element, surround nuclei with atomic charge Z > 2. For a given atom, their number varies with the number of core shell of the element and also with the local symmetry in the molecule. They are usually... 

SSD-V, f point at s -tl.997 amu bohr belonging to SSD-VI, g last point of the IRC, corresponding to the a-lactone species plus water, belonging to SSD-VII. The color code is as follow purple, core basins red, monosynaptic basins green, disynaptic basins blue, hydrogenated basins. Some basins are labeled throughout the figure... 

At the a-lactone, the first point of the SSD-I, fifteen basins have been found, corresponding with the four core basins, five disynaptic basins accounting for the... 

Figure 20.8a displays the ELF localization domains of the U02 " species at the 2c-B3LYP/ANO level of theory. The ELF topology yields six basins three core basins, C(U), C(Oi) and C(02), two valence basins associated to oxygen atoms, V (Oi) and V(02), and a free valence basin for uranium, V(U). The hierarchy of ELF domains can be used to get deeper insights into the nature of U-O interactions. The reduction diagram displays a unique pattern, as shown in Fig. 20.9. It reveals that U-O interactions cannot be understood as a pure ionic pairing picture [O ...

The basin of the penultimate (3rd) shell in fee Cu is populated by 16.40 e but the localization index is only 13.64. An analysis of the de-localization indices shows that it is mainly due to the electron sharing with its core basin (5 = 2.56) as well as nearest valence basins (5 = 0.26). Direct electron exchange with the penultimate shell of the nearest Cu atom is in order of magnitude smaller (5 = 0.03). 

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