Mass polarization effect, electronic state

Fermi level lies at = — 7.821 eV in this calculation. There is unfortunately no direct experimental evidence concerning the width of this band in (SN) . Therefore, we calculated some quantities from the band structure, which can be better related to experiment. For the effective electronic mass at the Fermi level we obtained 1.7me contrasted with the experimental value of Irrit deduced by Grant et alS from the analysis of polarized reflectivity spectra of single crystalline (SN) t. The density of states is calculated to be 0.14/(eV spin molecule) at the Fermi level this value is in quite good agreement with the value of 0.18/(eV spin molecule) found by Greene et from the contribution of the linear... 

When orbital overlap is not too marked and the bands are not very broad (cf. band width. Chapter 2) there is significant interaction between the lattice and the electrons. The electrons (or holes) then polarize their environment (see Section 5.3). The electron -I- distortion field state is known as a polaron. The semiconductor InSb is a typical example of a solid containing large polarons . Here the effective mass is increased very slightly, the mobility is not greatly reduced, and the band model for transport is a good approximation, in short the polarization effect is not too strong. Typical mobilities are of the order of 10 (alkaline earth titanates) and... 

In order to identify EPHs of the cell or electrode reactions from the experimental information, there had been two principal approaches of treatments. One was based on the heat balance under the steady state or quasi-stationary conditions [6,11, 31]. This treatment considered all heat effects including the characteristic Peltier heat and the heat dissipation due to polarization or irreversibility of electrode processes such as the so-call heats of transfer of ions and electron, the Joule heat, the heat conductivity and the convection. Another was to apply the irreversible thermodynamics and the Onsager s reciprocal relations [8, 32, 33], on which the heat flux due to temperature gradient, the component fluxes due to concentration gradient and the electric current density due to potential gradient and some active components transfer are simply assumed to be directly proportional to these driving forces. Of course, there also were other methods, for instance, the numerical simulation with a finite element program for the complex heat and mass flow at the heated electrode was also used [34]. 

The X-ray excitation process frequently is analyzed in terms of an excitonic electron hole pair (e.g. Cauchois and Mott 1949). The excitonic approach to X-ray absorption spectra accounts for the fact that the excited state is a hydrogen-like bound state. The X-ray exciton is different from the well-known optical excitons. In the latter cases the ejected electron polarizes a macroscopic fraction of the crystal-fine volume because the lifetime of optical excitations is in the order of lO s. The lifetime of the excited deep core level state, however, is in the order of 10 — 10 s, much too short to p-obe more than the direct vicinity of excited atom. Following Haken and Schottky (1958) the distance r between the ejected electron and core hole of an excited atom for E = 1 turns out to be r oc [h/(2m 0))] Here m denotes the effective mass of the ejected electron, to is the phonon frequency and is the dielectric constant. A numerical estimate yields r 10 A. Thus the information obtainable in an L, spectrum of the solid is very local the measurement probes essentially the 5d state of the absorbing atom as modified from the atomic 5d states by its immediate neighbors only. It is not suited to give information about extended Bloch states. On the other hand it is well suited to extract information about local correlations within the 5d conduction electrons, whose proper treatment is at the heart of the difficulty of the theory of narrow band materials and about chemical binding effects. 

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