Xie Weiwei, Holub Daniel, Kubař Tomáš, Elstner Marcus
Institute of Physical Chemistry, Karlsruhe Institute of Technology, Kaiserstrasse 12, 76131 Karlsruhe, Germany.
Institute of Biological Interfaces (IBG-2), Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany.
J Chem Theory Comput. 2020 Apr 14;16(4):2071-2084. doi: 10.1021/acs.jctc.9b01271. Epub 2020 Mar 26.
In the present study, several mixed quantum-classical (MQC) methods are applied to on-the-fly nonadiabatic molecular dynamics simulations of hole transport in molecular organic semiconductors (OSCs). The tested MQC methods contain the mean-field Ehrenfest (MFE), trajectory surface hopping (TSH) approaches based on Tully's fewest switches surface hopping (FSSH) and the global flux surface hopping (GFSH), the latter in the diabatic/adiabatic representation, and a Landau-Zener type trajectory surface hopping (LZSH). We also tested several correction schemes which were proposed to identify trivial crossings and to remove unphysical long-range charge transfers due to decoherence corrections. In addition, several cost-effective approaches for the nuclear velocity adjustment after an energy-allowed/energy-forbidden hop are investigated with respect to detailed balance and internal consistency conditions. To model a broad spectrum of OSCs with different charge transport characteristics, we derived from the anthracene structural model the construction of two additional models by uniformly scaling down the electronic couplings by the factors of 0.1 and 0.5. Anthracene shows a bandlike charge transport mechanism, characterized by slightly delocalized charge carriers 'diffusing' through the crystal. For smaller couplings, the mechanism changes to a hopping type, characteristically differing in the charge delocalization and temperature dependence. The MFE and corrected adiabatic TSH approaches are able to quantitatively reproduce the expected behavior, while the diabatic LZSH method fails for large couplings, as do approaches which are based on the hopping of localized charge between neighboring sites. Moreover, we find that while the hole mobility of the anthracene crystal simulated using the celebrated Marcus theory is in good agreement with the experimental value, its agreement has to be regarded as an accident due to the overestimation of the prefactor in the Marcus rate equation.
在本研究中，几种混合量子 - 经典（MQC）方法被应用于分子有机半导体（OSC）中空穴传输的即时非绝热分子动力学模拟。所测试的MQC方法包括平均场埃伦费斯特（MFE）、基于塔利最少开关表面跳跃（FSSH）的轨迹表面跳跃（TSH）方法以及全局通量表面跳跃（GFSH），后者采用 diabatic/adiabatic 表示形式，还有一种朗道 - 齐纳型轨迹表面跳跃（LZSH）。我们还测试了几种校正方案，这些方案旨在识别平凡交叉点并消除由于退相干校正导致的非物理长程电荷转移。此外，针对能量允许/能量禁止跳跃后的核速度调整，研究了几种符合细致平衡和内部一致性条件的经济有效方法。为了模拟具有不同电荷传输特性的广泛OSC，我们从蒽结构模型出发，通过将电子耦合均匀缩小0.1和0.5的因子，构建了另外两个模型。蒽表现出带状电荷传输机制，其特征是电荷载流子略有离域，“扩散”穿过晶体。对于较小的耦合，机制转变为跳跃型，在电荷离域和温度依赖性方面具有特征性差异。MFE和校正后的绝热TSH方法能够定量再现预期行为，而 diabatic LZSH方法在大耦合时失效，基于相邻位点之间局域电荷跳跃的方法也是如此。此外，我们发现，虽然使用著名的马库斯理论模拟的蒽晶体的空穴迁移率与实验值吻合良好，但其吻合必须被视为一种偶然，因为马库斯速率方程中的前置因子被高估了。
