Electron lattice coupling

The most striking implication of the electron lattice coupling in ID chains is the appearance of the semiconducting state the equal bond ID lattice (metallic state) is unstable (33) with respect to a lattice distorsion and this so called static Peierls instability is the origin of the opening of the intrinsic band gap at the edge of the B.Z. with an infinite density of states there and the presence of band alternation. 

By extension one may say that the power laws (5-7) which determine the magnitude of the linear and nonlinear optical coefficients are consequences of this strong electron-lattice coupling. We now make the conjecture that the time response of these coefficients is severely affected by the dynamics of the electron-lattice coupling in conjugated chains when two or more resonant chemical structures can coexist this is the case for many of the organic chains of Figure 2. 

The solid state polymerisation of diacetylenes (2) with U.V. radiation, heating or shear force is most indicative of the predominant influence of electron-lattice coupling. The details of the chemical changes that occur during th polymerisation process are crucial (2,40) but the overall description only needs part of this chemical information. The kinetics and thermodynamics of the polymerisation process using an elastic strain approach have been worked out in (41). 

It has been shown theoretically that an extra electron or hole added to a one-dimensional (ID) system will always self-trap to become a large polaron [31]. In a simple ID system the spatial extent of the polaron depends only on the intersite transfer integral and the electron-lattice coupling. In a 3D system an excess charge carrier either self-traps to form a severely locahzed small polaron or is not localized at all [31]. In the literature, as in the previous sections, it is frequently assumed for convenience that the wavefunction of an excess carrier in DNA is confined to one side of the duplex. This is, of course, not the case, although it is likely, for example, that the wavefunction of a hole is much larger on G than on the complementary C. In any case, an isolated DNA molecule is truly ID and theory predicts that an excess electron or hole should be in a polaron state. 

In summary, the magnetic and transport properties of the (Lai ),R),)o.7Cao.3Mn03 per-ovskites near the O -O phase boundary are extraordinarily sensitive to the tolerance factor t, the oxygen mass M0, temperature, and pressure as well as to magnetic and electric fields. This sensitivity can be attributed to strong electron-lattice coupling associated with not only order-... 

Keywords Electron-lattice coupling, phonons, spin-phonon interaction, vibronic state,... 

The first principles molecular dynamics simulation has been applied, based on the linearized-augmented-plane-wave (LAPW) method, to Seg and Seg+ clusters. The equilibrium structures have been obtained for Se8 and Se8+ clusters for the ionized cluster Seg-, a remarkable change from that for the neutral cluster has been found, which reflects the strong electron-lattice coupling in the cluster <1997MI1660, 1997MI75, 1997MI472>. 

W(0) is the asymptotic transfer probability for AE — 0 and ft a parameter determined by the strength of the electron-lattice coupling as well as by the nature of phonons involved. This expression is similar to that for multiphonon radiationless decay except for the fact that fi represents the coupling between the two species involved. 

Here g is the electron-lattice coupling constant, suffixes S and A are sensitizer and activator ions respectively, n is the number of phonons excited at the temperature of the system, hco is the phonon energy which contributes dominantly to these multiphonon processes and N is the number of phonons emitted in the processes, namely,... 

The ab initio calculations of polaron mobility on the basis of the Holstein-Peierls model including a nonlocal electron-lattice coupling (Hannewald and Bobbert [12,13] see references to earlier work therein) reproduced the temperature-... 

The metal to nonmetal transition, a basic electronic change, has proven surprisingly difficult to understand in detail. The underlying reason is the diametrically opposite modes of description natural for the metal (extended electronic states) and for the insulator (localized states, often with local constraints on electron number). The observed diversity of systems and phenomena indicates that a number of causes may be at work, e.g., disorder, short-range electron correlation, long-range Coulomb interaction, and electron lattice coupling. The effects... 

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