| Firstly, a bipolaron state in the pernigraniline-base polymer was investigated from an extended Ginder-Epstein model. The ring-angle configuration, bond-length-order waves (BOW), energy levels, absorption spectrum and charge distributions were obtained from the study. Then, they were compared with those in a polaron state. The excitation energy for a bipolaron is3.08eV. The depth of the relaxation of BOW for a bipolaron is twice that for a polaron. The maximum angle of the aromatic ring at the relaxation centre is as large as68.35°, which is more than twice of that in a polaron. The weak absorption associated the gap states is at1.6eV.Secondly, A bipolaron of the pernigraniline-base polymer under pressure was investigated from an extended Ginder-Epstein model, changing the parameter V2.0to express pressure of the polymer. While increasing pressure up to4.2GPa, excitation energy for a bipolaron reduced from3.45to1.23eV, meanwhile the gap and the relaxation disappeared from the study. The original band changed from style of a semiconductor to that of a metal. The results agree with the experimental observations that electrical conductivity is increasing with applied pressure until a saturated value. Our theory supports bipolaron-conduction mechanism for the polymer under pressures less than4.2GPa. Under higher pressure, carriers would be electrons as if in a metal. Lastly, mobility of an n-type bipolaron in the pernigraniline-base polymer under different pressure was investigated on the basis of an extended Ginder-Epstein model, in which parameter V2.0was varied to stand for pressure. The results showed that:mobility of the bipolaron increased firstly and then decreased, the saturated value was between4-5GPa. The results agree with the experimental observations that electrical conductivity is increasing with applied pressure until a saturated value. The conductivity of bipolaron come to a head321cm2/(V·s). Our theory supports bipolaron-conduction mechanism for the polymer. |
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