Revisiting electronic couplings and incoherent hopping models for electron transport in crystalline C60 at ambient temperatures
Revisiting electronic couplings and incoherent hopping models for electron transport in crystalline C60 at ambient temperatures
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DOI：
10.1039/c2cp41348e
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发表时间：
2012-01-01
影响因子：
3.3
通讯作者：
Blumberger, Jochen
中科院分区：
文献类型：
--
作者：
Oberhofer, Harald;Blumberger, Jochen
我们评估的非相干跳跃模型，以前被用来描述在室温下的晶体C-60中的电子输运的有效性。为此，我们提出了新的密度泛函理论为基础的计算定义这些模型的电子转移参数。具体而言，我们报告电子耦合矩阵元素的几个万配置，是热访问的C-60分子通过旋转扩散周围的晶格位置。我们发现，均方根波动的电子耦合矩阵元素（11毫电子伏）几乎一样大的平均值（14毫电子伏）和分布是很好地近似高斯。重要的是，由于C-60二聚体的重组能量很小（约为0.1 eV），ET对于大多数构型几乎是无活化的。然而，对于一个小的，但显着的分数的方向的耦合是如此之强的重组能量相比，没有电荷局域化的状态存在，如果考虑到原子核的零点运动的情况下，加剧。目前的计算表明，标准的跳跃模型不提供一个健全的描述电子输运在C-60，这可能是许多其他有机物的情况下，以及，需要的方法，直接解决电子动力学。
We assess the validity of incoherent hopping models that have previously been used to describe electron transport in crystalline C-60 at room temperature. To this end we present new density functional theory based calculations of the electron transfer parameter defining these models. Specifically, we report electronic coupling matrix elements for several ten thousand configurations that are thermally accessible to the C-60 molecules through rotational diffusion around their lattice sites. We find that the root-mean-square fluctuations of the electronic coupling matrix element (11 meV) are almost as large as the average value (14 meV) and that the distribution is well approximated by a Gaussian. Importantly, due to the small reorganisation energy of the C-60 dimer (approximate to 0.1 eV), the ET is almost activationless for the majority of configurations. Yet, for a small but significant fraction of orientations the coupling is so strong compared to reorganisation energy that no charge-localised state exists, a situation that is aggravated if zero-point motion of the nuclei is taken into account. The present calculations indicate that standard hopping models do not provide a sound description of electron transport in C-60, which might be the case for many other organics as well, and that approaches are needed that solve the electron dynamics directly.