Department of Chemistry and Centre for Scientific Computing, University of Warwick, Coventry CV4 7AL, United Kingdom.
Phys Rev Lett. 2015 Jan 16;114(2):026402. doi: 10.1103/PhysRevLett.114.026402. Epub 2015 Jan 14.
We show that the excitonic coupling in molecular crystals undergoes a very large fluctuation at room temperature as a result of the combined thermal motions of the nuclei. This observation dramatically affects the description of exciton transport in organic crystals and any other phenomenon (like singlet fission or exciton dissociation) that originates from an exciton in a molecular crystal or thin film. This unexpected result is due to the predominance of the short-range excitonic coupling mechanisms (exchange, overlap, and charge-transfer mediated) over the Coulombic excitonic coupling for molecules in van der Waals contact. To quantify this effect we develop a procedure to evaluate accurately the short-range excitonic coupling (via a diabatization scheme) along a molecular dynamics trajectory of the representative molecular crystals of anthracene and tetracene.
我们表明，由于原子核的热运动，室温下分子晶体中的激子耦合会发生非常大的波动。这一观察结果极大地影响了有机晶体中激子输运的描述以及任何其他源于分子晶体或薄膜中激子的现象（如单重态裂变或激子解离）。这一意外结果是由于范德华接触的分子中短程激子耦合机制（交换、重叠和电荷转移介导）相对于库仑激子耦合占主导地位。为了定量描述这种效应，我们开发了一种方法，通过分子动力学轨迹对蒽和并四苯的代表性分子晶体进行精确评估短程激子耦合（通过二价化方案）。
