Electron localization function analysis

Fig. 5. Electron Localization Function analysis for the model compound 2 Pa (ring bonds in plane of paper)...

Pilme J, Piquemal J-P (2008) Advancing beyond charge analysis using the electronic localization function Chemically intuitive distribution of electrostatic moments. J Comput Chem 29 1440... 

Silvi B, Savin A (1994) Classification of chemical bonds based on topological analysis of electron localization functions. Nature 371 683... 

The study of chemical reactions requires the definition of simple concepts associated with the properties ofthe system. Topological approaches of bonding, based on the analysis of the gradient field of well-defined local functions, evaluated from any quantum mechanical method are close to chemists intuition and experience and provide method-independent techniques [4-7]. In this work, we have used the concepts developed in the Bonding Evolution Theory [8] (BET, see Appendix B), applied to the Electron Localization Function (ELF, see Appendix A) [9]. This method has been applied successfully to proton transfer mechanism [10,11] as well as isomerization reaction [12]. The latter approach focuses on the evolution of chemical properties by assuming an isomorphism between chemical structures and the molecular graph defined in Appendix C. 

The question remains whether the nodal planes, essential for the qualitative analysis, remain in the more advanced calculations of wavefunctions. To test this point, the electronic localization function (ELF) as implemented by B. Silvi and A. Savin [24] is used. In Figure 3 we summarize the results. 

A theoretical study on the reaction mechanism for the Bergman cyclization from the perspective of the Electron Localization Function and Catastrophe Theory has been reported.175 The authors argue that topological analysis of electron localization function can be used to complement the molecular orbital- or valence bond-based methods. 

Several alternatives to the Mulliken population have been presented that attempt to provide more rigorous estimates of the charges on atoms in molecules or clusters although not all have been applied in chemisorption and catalysis. We quote the Natural Bond Order analysis, and the elegant topological analysis of the electron density or of the electron localization function, ELF, introduced by Becke and Edgecombe. " ELF analysis has... 

A topological analysis of the electron localization function (ELF) provides an unbiased description of the chemical bond [28]. The ELF contours for O adsorption on the M-top site are reported on Fig. 6.6 for a representative TMC of groups 4, 5 and 6 of the Periodic Table. These results do not exhibit any region with a large... 

A double Rydberg anion (DRA) consists of a stable cationic core and two electrons in a diffuse Rydberg orbital. These anions correspond to a local minimum on a potential energy surface where more stable isomers may exist. Experimental and theoretical works have contributed to a better understanding of the unusual electronic structure of these molecules. With electron propagator calculations and analysis of the electron localization function, some relationships between electronic structure and reactivity in DRAs are considered. 

These works established the existence of a novel variety of electron pair in DRAs. Extensions of traditional electron pair concepts are clearly needed for these anions. The electron localization function (ELF) 19 is an interesting and robust descriptor of chemical bonding, which has been successfully applied to a wide variety of molecular systems.20-24 This function, which is based on a topological analysis of a quantum function related to Pauli repulsion, describes the degree of localization (or delocalization) of electron pairs within the molecular space. 

Analysis of the electron localization function for geometries of the same reaction path provides an alternative, but compatible, perspective on the evolution of electronic structure. The novel asynaptic basin of the DRA, which represents a pair of electrons that is delocalized over the periphery of the ammonium cation core, is transformed into a conventional, monosynaptic basin that is associated with the departing hydrogen at the geometries near the transition state. After the transition state, the NH system may be described as a hydride-ammonia complex. 

Further investigation of 2 Pb via analysis of the Laplacian of the electron density and the electron localization function (ELF) [34] reveals a strong banana P-P-bond with large p-character (the bond ellipticity is 0.45) in the plane of the ring, and partial double bond character (Wiberg bond indices = 1.2) for the PC-bonds (Fig. 5). 

The purpose of the topological analysis of the electron localization function is to provide a sound mathematical model of the Lewis , and theories which... 

S. Noury, X. Krokidis, F. Fuster, and B. Silvi, Computational tools for the electron localization function topological analysis, Comput. Chem. 23, 597-604 (1999). 

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