High-Pressure Induced Quenching of Polaron in the Emeraldine-Base Polymer
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摘要: 利用改进的Ginder-Epstein模型，研究了高压下苯胺绿聚合物的空穴极化子态。发现高压下极化子晶格畸变被削弱直至消失，而格点电子密度由局域分布趋于整链均摊。极化子激发能随体系受压而降低，最终导致载流子的相对浓度上升了12个数量级，聚合物由半导体转变成为金属型导体, 理论临界压强为13.76 GPa。达到此压强后，体系只存在价带顶到导带底的电子跃迁，其光吸收峰为0.5 eV，可以作为压强达到饱和值的光谱学证据。Abstract: A hole polaron in the Emeraldine-base polymer under pressure was investigated on the basis of an extended Ginder-Epstein model.We found:the polaron relaxasion was weakened to disappear and the original local charge tended to distribute on the whole chain; Because of the pressure' excitation energy got lower so that the concentration of carriers got higher up to 12 orders of magnitude.In fact, we met a semiconductor-metal transition, our critic pressure was 13.76 GPa.Upon the pressure, there were electronic transitions from the top of the valence band to the bottom of the conduction band, the caculated peak of absorption was at 0.5 eV, which would be a spectrum evidence for the semiconductor-metal transition.
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Key words:
- high-pressure /
- emeraldine-base /
- polaron /
- conductivity /
- polymer
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图 7 理论光吸收谱随压强的变化
Figure 7. Calculated absorption spectra of the polymer with the increasing pressure
表 1 极化子的激发能、相对浓度随压强的变化
Table 1. Energy of excitation, concentration for the polaron versus pressure
p/(GPa) Eexc/(eV) n/n0 0.99 1.88 1.62×10-16 3.51 1.78 1.08×10-15 5.18 1.68 7.69×10-15 6.35 1.57 5.68×10-14 7.31 1.47 4.34×10-13 8.14 1.36 3.43×10-12 8.87 1.25 2.71×10-11 9.56 1.09 6.49×10-10 10.19 0.98 5.08×10-9 10.78 0.90 2.63×10-8 11.34 0.80 1.83×10-7 11.86 0.68 1.89×10-6 12.37 0.59 9.19×10-6 12.85 0.57 1.48×10-5 13.31 0.48 8.98×10-5 13.76 0.37 6.59×10-4 14.19 0.37 6.59×10-4 14.61 0.37 6.59×10-4 15.01 0.37 6.59×10-4 
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