State Key Laboratory of Physical Chemistry of Solid Surfaces, and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, People's Republic of China.
J Chem Phys. 2011 Oct 7;135(13):134110. doi: 10.1063/1.3644965.
A time-dependent wavepacket diffusion method is proposed to deal with charge transport in organic crystals. The electron-phonon interactions in both site energies and electronic couplings are incorporated by the time-dependent fluctuations which are generated from the corresponding spectral density functions. The numerical demonstrations reveal that the present approach predicts the consistent charge carrier dynamics with the rigorous quantum approaches. In addition, the diffusion coefficients obtained from the Marcus formula are well reproduced at the weak electronic coupling and high temperature limits. It is also found that the charge mobility feature of the crossover from the band-like to the hopping-type cannot be predicted from the fluctuations induced by the linear electron-phonon interactions with an Ohmic spectral density; however, it indeed appears as the electronic coupling fluctuation exponentially depends on the nuclear coordinates. Finally, it should be noted that although the present approach neglects the imaginary fluctuation, it essentially incorporates the coherent motion of the charge carrier and quantum effect of the phonon motion with a broad regime of the fluctuations for symmetric systems. Besides, the approach can easily be applied to systems having thousands of sites, which allows one to investigate charge transport in nanoscale organic crystals.
提出了一种时变波包扩散方法来处理有机晶体中的电荷输运。通过由相应的光谱密度函数产生的时变涨落，将在位置能量和电子耦合中的电子-声子相互作用纳入其中。数值演示表明，该方法预测的电荷载流子动力学与严格的量子方法一致。此外，在弱电子耦合和高温极限下，从马库斯公式得到的扩散系数得到了很好的再现。还发现，从具有欧姆光谱密度的线性电子-声子相互作用引起的涨落，无法预测从能带型到跳跃型的电荷迁移特征的转变；然而，当电子耦合涨落随核坐标呈指数增长时，这种转变确实会出现。最后，应当指出，尽管该方法忽略了虚涨落，但它实际上包含了电荷载流子的相干运动和声子运动的量子效应，以及对于对称系统的涨落的宽范围。此外，该方法可以很容易地应用于具有数千个位置的系统，从而可以研究纳米尺度有机晶体中的电荷输运。
