Polaron energy/mobility

With mixed-valence compounds, charge transfer does not require creation of a polar state, and a criterion for localized versus itinerant electrons depends not on the intraatomic energy defined by U , but on the ability of the structure to trap a mobile charge carrier with a local lattice deformation. The two limiting descriptions for mobile charge carriers in mixed-valence compounds are therefore small-polaron theory and itinerant-electron theory. We shall find below that we must also distinguish mobile charge carriers of intennediate character. 

Turning to the calculations of polaron mobility in Sect. 2.5, we find that, although a stationary polaron can form with the wavefunction extending over an arbitrary sequence of bases, in the absence of an electric field, or in a small electric field, the polaron cannot move far unless the DNA is made up of the same base pair repeated. This result is for zero temperature, of course, not allowing thermal energy that makes possible the transition dis-... 

After a photon has excited the conjugated polymer to form an exciton, the C60 accepts one electron due to its high electron affinity and establishes the anion Cg0. What is left on the polymer chain is a cation radical, i.e., a positive polaron, as depicted in Fig. 1.14, which is a mobile charge carrier that can move along the polymer backbone. This transfer is an exothermal reaction, where energy from the system is released. 

A polaron is a fermion quasi-particle consisting of an anion (or cation) defect with an associated polarized Gegenion (= counterion) atmosphere or polarization this is an excited state of the system, with energy intermediate between the valence band and the conduction band. Its mobility within the lattice is due to the fact that there is a low energy barrier for the polarization to move from one site to the next. Polarons are the dominant excitations in conducting polymers. 

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