Xie Weiwei, Sapunar Marin, Došlić Nađa, Sala Matthieu, Domcke Wolfgang
Department of Chemistry, Technical University of Munich, Lichtenbergstr. 4, 85747 Garching, Germany.
Department of Physical Chemistry, Ruđer Bošković Institute, HR-10000 Zagreb, Croatia.
J Chem Phys. 2019 Apr 21;150(15):154119. doi: 10.1063/1.5084961.
Trajectory surface hopping (TSH) methods have been widely used to study photoinduced nonadiabatic processes. In the present study, nonadiabatic dynamics simulations with the widely used Tully's fewest switches surface hopping (FSSH) algorithm and a Landau-Zener-type TSH (LZSH) algorithm have been performed for the internal conversion dynamics of pyrazine. The accuracy of the two TSH algorithms has been critically evaluated by a direct comparison with exact quantum dynamics calculations for a model of pyrazine. The model comprises the three lowest excited electronic states (B(nπ), A(nπ), and B(ππ)) and the nine most relevant vibrational degrees of freedom. Considering photoexcitation to the diabatic B(ππ) state, we examined the time-dependent diabatic and adiabatic electronic population dynamics. It is found that the diabatic populations obtained with both TSH methods are in good agreement with the exact quantum results. Fast population oscillations between the B(nπ) and A(nπ) states, which reflect nonadiabatic electronic transitions driven by coherent dynamics in the normal mode Q, are qualitatively reproduced by both TSH methods. In addition to the model study, the TSH methods have been interfaced with the second-order algebraic diagrammatic construction ab initio electronic-structure method to perform full-dimensional on-the-fly nonadiabatic dynamics simulations for pyrazine. It is found that the electronic population dynamics obtained with the LZSH method is in excellent agreement with that obtained by the FSSH method using a local diabatization algorithm. Moreover, the electronic populations of the full-dimensional on-the-fly calculations are in excellent agreement with the populations of the three-state nine-mode model, which confirms that the internal conversion dynamics of pyrazine is accurately represented by this reduced-dimensional model on the time scale under consideration (200 fs). The original FSSH method, in which the electronic wave function is propagated in the adiabatic representation, yields less accurate results. The oscillations in the populations of the diabatic B(nπ) and A(nπ) states driven by the mode Q are also observed in the full-dimensional dynamics simulations.
轨迹表面跳跃（TSH）方法已被广泛用于研究光诱导的非绝热过程。在本研究中，使用广泛应用的塔利最少开关表面跳跃（FSSH）算法和朗道 - 齐纳型TSH（LZSH）算法对吡嗪的内转换动力学进行了非绝热动力学模拟。通过与吡嗪模型的精确量子动力学计算直接比较，对这两种TSH算法的准确性进行了严格评估。该模型包含三个最低激发电子态（B(nπ)、A(nπ)和B(ππ)）以及九个最相关的振动自由度。考虑到光激发到非绝热的B(ππ)态，我们研究了随时间变化的非绝热和绝热电子布居动力学。结果发现，两种TSH方法得到的非绝热布居与精确量子结果吻合良好。两种TSH方法都定性地再现了B(nπ)和A(nπ)态之间快速的布居振荡，这反映了由简正模式Q中的相干动力学驱动的非绝热电子跃迁。除了模型研究外，TSH方法还与二阶代数图示构建从头算电子结构方法相结合，对吡嗪进行全维即时非绝热动力学模拟。结果发现，使用LZSH方法得到的电子布居动力学与使用局域非绝热化算法的FSSH方法得到的结果非常吻合。此外，全维即时计算的电子布居与三态九模模型的布居非常吻合，这证实了在所考虑的时间尺度（200 fs）下，该降维模型准确地描述了吡嗪的内转换动力学。原始的FSSH方法，其中电子波函数在绝热表象中传播，得到的结果准确性较低。在全维动力学模拟中也观察到了由模式Q驱动的非绝热B(nπ)和A(nπ)态布居的振荡。
