Solids electronic localization

In this second edition the text has been revised and new scientific findings have been taken into consideration. For example, many recently discovered modifications of the elements have been included, most of which occur at high pressures. The treatment of symmetry has been shifted to the third chapter and the aspect of symmetry is given more attention in the following chapters. New sections deal with quasicrystals and other not strictly crystalline solids, with phase transitions and with the electron localization function. There is a new chapter on nanostructures. Nearly all figures have been redrawn. 

Savin A, Had OJ, Andersen J, Preuss H,Von Schering HG, Angew (1992) Electron localization in solid-state. Structures for the elements the diamond. Chem Int 31 187... 

In the Introduction the problem of construction of a theoretical model of the metal surface was briefly discussed. If a model that would permit the theoretical description of the chemisorption complex is to be constructed, one must decide which type of the theoretical description of the metal should be used. Two basic approaches exist in the theory of transition metals (48). The first one is based on the assumption that the d-elec-trons are localized either on atoms or in bonds (which is particularly attractive for the discussion of the surface problems). The other is the itinerant approach, based on the collective model of metals (which was particularly successful in explaining the bulk properties of metals). The choice between these two is not easy. Even in contemporary solid state literature the possibility of d-electron localization is still being discussed (49-51). Examples can be found in the literature that discuss the following problems high cohesion energy of transition metals (52), their crystallographic structure (53), magnetic moments of the constituent atoms in alloys (54), optical and photoemission properties (48, 49), and plasma oscillation losses (55). 

In this section, several studies of model molecular solids are reviewed that shed some light on the origin of the line widths and gas-to-solid spectral energy shifts in the UPS spectra of molecular solids. First, examples are given of contributions to the solid state UPS line broadening. A following discussion deals with the energy shift and electronic localization issues, which are directly related. 

Intermolecular relaxation effects are a central issue in the interpretation of the ultraviolet photoelectron spectroscopy (UPS) of molecular solids. These relaxation effects result in several significant characteristics of UPS valence spectra, intermolecular relaxation phenomena lead to localized electron molecular-ion states, which are responsible for rigid gas-to-solid molecular spectral energy shifts, spectral line broadening, and dynamic electronic localization effects in aromatic pendant group polymers. 

Finally a method which shows promise for the future is d5mamic mean field theory. Dynamical mean field theory uses an approximation to the local spectral density functional (rather than energy density functional) and a set of correlated local orbitals. For solids this local description is combined with a periodic description such as DFT using EDA to provide a method of dealing with both localised and delocalised electrons." Anisimov et applied this method to the photo-... 

Figure 21 shows temperature dependence of electrical conductivity and magnetic susceptibility of MEM(Af-methyl-iV-ethyl-morpholinium)-(TCNQ)2 [70]. At about 335 K it undergoes a metal-insulator transition accompanied by the onset of a two-fold superstructure and a temperature dependent magnetic susceptibility characteristic of localized moments. It is considered as depicted in Fig. 22(a) that a dimerized TCNQ accepts an electron localized by, for example, the Mott transition or the Wigner crystallization. The solid curve shown in Fig. 21(b) denotes the theoretical prediction for the magnetic susceptibility of a one-... 

Fig. 2. At the top is a schematic view of the electrons (solid points) localized along the stacks in Cs2TCNQ and the two types of charge transfer excitations, A and 15. Below are the absorption spectra for a wide variety of powdered TCNQ salts, dispersed into KBr disks. (After TSK, Ref. 9).

The content is essentially based on the results first developed in quantum theory of solids (Table 2), namely omnidirectional band gaps in electron energy spectrum and electron localization phenomena. Probably, transmission properties of fractal structures [12] is the only example of nanophotonic... 

Savin, A. (1993) Electron Localization Function (ELF) in molecules and solids. Second International Conference on Inorganic Chemistry, Stuttgart, Germany. Kohout, M., and Savin, A. (1996) Influence of the core-valence separation on the Electron Localization Function. Int. J. Quant. Chem. (in press)... 

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