第一性原理研究有机分子晶体中电声子耦合的压强效应

First-princples study of the electron-phonon couplings in organic molecular crystals

电声子耦合系数是决定有机分子体系电荷传导过程的最重要因素之一,研究电声子耦合对理解有机分子晶体中的本征电荷传输机制有重要的意义.从实验得到的晶体结构出发,使用密度泛函理论计算出电子结构和声子模式,再投影到紧束缚模型,通过数值拟合和有限差分,计算出各个声子模的电声子耦合系数,进一步还可以研究随压强变化的关系.以萘晶体为例,计算表明,声子频率随压强增加,但电声耦合强度随压强增大而减小,对迁移率起到促进作用.

The electron-phonon couplings are important factors to detemaine the charge transport properties in organic molecular systems. Therefore, it can help us to understand the intrinsic charge transport mechanism in organic molecular crystals. Starting from the experimental lattice parameters, we calculate the electronic structures and the phonon modes with density functional theory, then we evaluate the electron-phonon coupling constants by projecting the first-principles to tight binding model and by finite derivatives. The relationship between electron-phonon couplings and pressure have been analyzed. While the phonon frequency is found to increase with pressure, the electron-phonon coupling strength is found to decrease with pressure.