Premium
Conductivity in polyacetylene. VI. Semiconductor—Metal transition of alkali‐doped polymer
Author(s) -
Larsson Sven,
RodriguezMonge Lucia
Publication year - 1997
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/(sici)1097-461x(1997)63:3<655::aid-qua7>3.0.co;2-v
Subject(s) - alkali metal , polyacetylene , chemistry , polaron , polarizability , doping , conductivity , electronegativity , electron , semiconductor , valence (chemistry) , valence electron , polymer , atomic physics , condensed matter physics , materials science , physics , molecule , organic chemistry , optoelectronics , quantum mechanics
A local model is set up for the conductivity in alkali‐doped polyacetylene (PA) based on results of ab initio and semiempirical calculations. At low doping levels, solitons and polarons appear naturally in the (nondegenerate) ground state. Alkali atoms donate their valence electrons to neutral solitons, which have the highest electron affinity in the PA structure. Due to the high polarizability of the PA chains, there is a charge buildup on a few carbon atoms close to the alkali ion. At the same time, a new soliton, screened from the alkali ion, is formed some distance away from the latter. This solition may migrate through the PA polymer partly by hopping for one chain segment to another (E a ≥ 0.15 eV) and partly by soliton motion. In the calculation of the spectra, we used geometry‐optimized structures and configuration interaction (i.e., taking into account electron‐lattice interaction and explicit Coulomb correlation) and obtained good agreement with experimental spectra. As the concentration of alkali is increased, absorption occurs at energies below 1 eV. At higher doping levels, corresponding to a few mol%, the electrons delocalize over many alkali spacings and the trapping capability of the polymer decreases the conductivity becomes bandlike. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 655–665, 1997