利用基于直接动力学的轨线面跳跃方法处理非绝热过程

势能面交叉引起的非绝热过程广泛存在于光化学和光物理中。对这一过程进行描述是理论化学的重要挑战之一。非绝热过程涉及原子核与电子之间的耦合运动,因此量子化学的基本假设之一"玻恩-奥本海默"近似被打破,所以对其进行描述需要发展新的动力学理论方法。在这些方法中,Tully发展的最少轨线面跳跃方法凭借易于程序化、便于计算等优点已经发展成为处理非绝热问题的主要动力学方法之一。其中原子核以经典的方式在单一势能面上进行演化,电子以量子的方式沿着同一轨线进行演化。在整个演化过程中,非绝热跃迁通过轨线在不同势能面间的跃迁来描述,其中跳跃发生的几率与电子的演化有关。如果将该方法与从头算直接动力学相结合,可以在全原子水平上研究实际分子体系的非绝热动力学,给出其激发态寿命、非绝热动力学中分子的主要运动方式、反应通道以及分支比等重要信息。本文旨在讨论最少面跳跃直接动力学方法研究非绝热问题的一些进展,包括动力学基本理论,特别关注将最少面跳跃方法和直接动力学结合的数值实现细节,同时讨论该方法在研究实际体系当中的一些应用,并对轨线面跳跃方法下一步发展的一些方向进行合理的展望。     

Ab Initio Nonadiabatic Dynamics of Semiconductor Materials via Surface Hopping Method

Photoinduced carrier dynamic processes are without doubt the main driving force responsible for the efficient performance of semiconductor nanomaterials in applications like photoconversion and photonics. Nevertheless, establishing theoretical insights into these processes is computationally challenging owing to the multiple factors involved in the processes, namely reaction rate, material surface area, material composition etc. Modelling of photoinduced carrier dynamic processes can be performed via nonadiabatic molecular dynamics (NA-MD) methods, which are methods specifically designed to solve the time-dependent Schrodinger equation with the inclusion of nonadiabatic couplings. Among NA-MD methods, surface hopping methods have been proven to be a mighty tool to mimic the competitive nonadiabatic processes in semiconductor nanomaterials, a worth noticing feature is its exceptional balance between accuracy and computational cost. Consequently, surface hopping is the method of choice for modelling ultrafast dynamics and more complex phenomena like charge separation in Janus transition metal dichalcogenides-based van der Waals heterojunction materials. Covering latest stateof-the-art numerical simulations along with experimental results in the field, this review aims to provide a basic understanding of the tight relation between semiconductor nanomaterials and the proper simulation of their properties via surface hopping methods. Special stress is put on emerging state-ot-the-art techniques. By highlighting the challenge imposed by new materials, we depict emerging creative approaches, including high-level electronic structure methods and NA-MD methods to model nonadiabatic systems with high complexity.     

Functional and Basis Set Dependence for Time-Dependent Density Functional Theory Trajectory Surface Hopping Molecular Dynamics: Cis-Azobenzene Photoisomerization

Within three functionals (TD-B3LYP, TD-BHandHLYP, and TD-CAM-B3LYP) in combination with four basis sets (3-21g, 6-31g, 6-31g(d), and cc-pvdz), global switching (GS) trajectory surface hopping molecular dynamics has been performed for cis-to-trans azobenzene photoisomerization up to the S₁(nπ*) excitation. Although all the combinations show artificial double-cone structure of conical intersection between ground and first excited states, simulated quantum yields and lifetimes are in good agreement with one another; 0.6 (±5%) and 40.5 fs (±10%) by TD-B3LYP, 0.5 (±10%) and 35.5 fs (±4%) by TD-BHandHLYP, and 0.44 (±9%) and 35.2 fs (±10%) by TD-CAM-B3LYP. By analyzing distributions of excited-state population decays, hopping spots, and typical trajectories with performance of 12 functional/basis set combinations, it has been concluded that functional dependence for given basis set is slightly more sensitive than basis set dependence for given functional. The present GS on-the-fly time-dependent density functional theory (TDDFT) trajectory surface hopping simulation can provide practical benchmark guidelines for conical intersection driven excited-state molecular dynamics simulation involving in large complex system within ordinary TDDFT framework. © 2019 Wiley Periodicals, Inc.     

Interpretation of Adiabatic and Diabatic Populations from Trajectories of Branching Corrected Surface Hopping

The branching corrected surface hopping (BCSH) has been demonstrated as a robust approach to improve the performance of the traditional fewest switches surface hopping (FSSH) for nonadiabatic dynamics simulations of standard scattering problems [J. Chem. Phys. 150 , 164101 (2019)]. Here, we study how reliable populations of both adiabatic and diabatic states can be interpreted from BCSH trajectories. Using exact quantum solutions and FSSH results as references, we investigate a series of one-dimensional two-level scattering models and illustrate that excellent time-dependent populations can be obtained by BCSH. Especially, we show that different trajectory analysis strategies produce noticeable differences in different representations. Namely, the method based on active states performs better to get populations of adiabatic states, while the method based on wavefunctions produces more reliable results for populations of diabatic states.     

Theories and Applications of Mixed Quantum-Classical Non-adiabatic Dynamics

Electronically non-adiabatic processes are essential parts of photochemical process, collisions of excited species, electron transfer processes, and quantum information processing. Various non-adiabatic dynamics methods and their numerical implementation have been developed in the last decades. This review summarizes the most significant development of mixed quantum-classical methods and their applications which mainly include the Liouville equation, Ehrenfest mean-field, trajectory surface hopping, and multiple spawning methods. The recently developed quantum trajectory mean-field method that accounts for the decoherence corrections in a parameter-free fashion is discussed in more detail.     

An ab initio molecular dynamics study on the dissociative recombination reaction of HD2O+ + e−

An ab initio molecular dynamics simulations have been carried out for the dissociative recombination reaction of the deuterium-substituted hydronium cation, HD₂O⁺ + e ⁻, at the state-averaged multiconfigurational self-consistent field level. In the present simulations, five electronic states of HD₂O were included explicitly, and nonadiabatic transitions among adiabatic electronic states were taken into account by the Tully’s fewest switches algorithm. It is shown that the dominant products, OD + D + H, were generated in 63% of trajectories, while the products, OH + 2D, were generated in only 11% of trajectories, indicating that the release of a light fragment H is favored over the release of a heavy fragment D. This result is in conformity with the observation that there is a larger amount of deuterium substituted species than the non-substituted species in the interstellar space. Contribution to the Mark S. Gordon 65th Birthday Festschrift Issue.     

Photodynamics of Methyl-Vinyl Criegee Intermediate: Different Conical Intersections Govern the Fates of Syn/Anti Configurations

Methyl vinyl ketone oxide, an unsaturated four-carbon Criegee intermediate produced from the ozonolysis of isoprene has been recognized to play a key role in determining the tropospheric OH concentration. It exists in four configurations (\begin{document}$ anti $\end{document}-\begin{document}$ anti $\end{document}, \begin{document}$ anti $\end{document}-\begin{document}$ syn $\end{document}, \begin{document}$ syn $\end{document}-\begin{document}$ anti $\end{document}, and \begin{document}$ syn $\end{document}-\begin{document}$ syn $\end{document}) due to two different substituents of saturated methyl and unsaturated vinyl groups. In this study, we have carried out the electronic structure calculation at the multi-configurational CASSCF and multi-state MS-CASPT2 levels, as well as the trajectory surface-hopping nonadiabatic dynamics simulation at the CASSCF level to reveal the different fates of \begin{document}$ syn $\end{document}/\begin{document}$ anti $\end{document} configurations in photochemical process. Our results show that the dominant channel for the S\begin{document}$ _1 $\end{document}-state decay is a ring closure, isomerization to dioxirane, during which, the \begin{document}$ syn $\end{document}(C\begin{document}$ - $\end{document}O) configuration with an intramolecular hydrogen bond shows slower nonadiabatic photoisomerization. More importantly, it has been found for the first time in photochemistry of Criegee intermediate that the cooperation of two heavy groups (methyl and vinyl) leads to an evident pyramidalization of C3 atom in methyl-vinyl Criegee intermediate, which then results in two structurally-independent minimal-energy crossing points (CIs) towards the \begin{document}$ syn $\end{document}(C\begin{document}$ - $\end{document}O) and \begin{document}$ anti $\end{document}(C\begin{document}$ - $\end{document}O) sides, respectively. The preference of surface hopping for a certain CI is responsible for the different dynamics of each configuration.     

Simulating quantum dynamics in classical environments

Methods for simulating the dynamics of composite systems, where part of the system is treated quantum mechanically and its environment is treated classically, are discussed. Such quantum–classical systems arise in many physical contexts where certain degrees of freedom have an essential quantum character while the other degrees of freedom to which they are coupled may be treated classically to a good approximation. The dynamics of these composite systems are governed by a quantum–classical Liouville equation for either the density matrix or the dynamical variables which are operators in the Hilbert space of the quantum subsystem and functions of the classical phase space variables of the classical environment. Solutions of the evolution equations may be formulated in terms of surface-hopping dynamics involving ensembles of trajectory segments interspersed with quantum transitions. The surface-hopping schemes incorporate quantum coherence and account for energy exchanges between the quantum and classical degrees of freedom. Various simulation algorithms are discussed and illustrated with calculations on simple spin-boson models but the methods described here are applicable to realistic many-body environments.     

WavePacket: A Matlab package for numerical quantum dynamics. III. Quantum-classical simulations and surface hopping trajectories

WavePacket is an open-source program package for numerical simulations in quantum dynamics. Building on the previous Part I (Schmidt and Lorenz, Comput. Phys. Commun. 2017, 213, 223] and Part II (Schmidt and Hartmann, Comput. Phys. Commun. 2018, 228, 229] which dealt with quantum dynamics of closed and open systems, respectively, the present Part III adds fully classical and mixed quantum-classical propagation techniques to WavePacket. There classical phase-space densities are sampled by trajectories which follow (diabatic or adiabatic) potential energy surfaces. In the vicinity of (genuine or avoided) intersections of those surfaces, trajectories may switch between them. To model these transitions, two classes of stochastic algorithms have been implemented: (1) Tully's fewest switches surface hopping and (2) Landau–Zener-based single switch surface hopping. The latter one offers the advantage of being based on adiabatic energy gaps only, thus not requiring nonadiabatic coupling information any more. The present work describes the MATLAB version of WavePacket 6.1.0, which is essentially an object-oriented rewrite of previous versions, allowing to perform fully classical, quantum-classical and quantum-mechanical simulations on an equal footing, that is, for the same physical system described by the same WavePacket input. The software package is hosted and further developed at the Sourceforge platform, where also extensive Wiki-documentation as well as numerous worked-out demonstration examples with animated graphics are available. © 2019 Wiley Periodicals, Inc.     

Local Control Theory in Trajectory Surface Hopping Dynamics Applied to the Excited‐State Proton Transfer of 4‐Hydroxyacridine

The application of local control theory combined with nonadiabatic ab initio molecular dynamics to study the photoinduced intramolecular proton transfer reaction in 4‐hydroxyacridine was investigated. All calculations were performed within the framework of linear‐response time‐dependent density functional theory. The computed pulses revealed important information about the underlying excited‐state nuclear dynamics highlighting the involvement of collective vibrational modes that would normally be neglected in a study performed on model systems constrained to a subset of the full configuration space. This study emphasizes the strengths of local control theory for the design of pulses that can trigger chemical reactions associated with the population of a given molecular excited state. In addition, analysis of the generated pulses can help to shed new light on the photophysics and photochemistry of complex molecular systems.     

TiO2表面光催化基元过程

在过去的几十年里,得益于二氧化钛(TiO₂)作为光催化剂在光催化分解水、污染物降解方面的潜在应用,人们对TiO₂光催化剂的开发、改良以及TiO₂表面光催化机理的基础研究方面都投入了巨大的精力。因此,在超高真空环境下,利用不同的实验和理论方法,人们对TiO₂表面(特别是金红石TiO₂(110)表面)的热催化和光催化过程进行了大量的研究,以此来获得上述重要反应中的一些机理性的信息。本文中,将从TiO₂的物质结构以及电子结构开始,然后着重介绍TiO₂表面光生电荷(电子和空穴)的传输、捕获以及电子转移动力学方面的进展。在此基础上,总结了甲醇在金红石TiO₂(110)、TiO₂(011)以及锐钛矿TiO₂(101)表面光化学基元反应过程的一些实验结果。这些结果不仅能增进我们对表面光催化基元过程的认识,同时也能激励我们进一步去研究表面光催化基元过程。最后,基于现有光化学实验结果,简短地讨论了我们对光催化反应机理的一点看法,并提出了一个可能的光催化模型,这可以引起人们对光催化反应机理更全面的思考。     

Trajectory surface hopping molecular dynamics on Chemiluminescence of cyclic peroxides

Chemiluminescence (CL) of peroxides is one of the most highly sensitive and most useful analytical techniques. Although the mechanisms of CL were studied experimentally and theoretically in the past decades, the chemiexcitation that a ground-state specie being excited from its electronic ground state to yield excited-state products by a chemical reaction is still not completely understood. Direct dynamics simulation on CL reaction which takes into account the full complexity of the relevant potential energy surface characterizes nonadiabatic processes involved in chemiexcitation and could provide access not only to the available reaction channels but also to statistical quantities such as reaction times and quantum yields. In the last decade, the trajectory surface hopping (TSH) molecular dynamics (MD) which is one of the mixed quantum-classical approaches is hence adopted to simulate the nonadiabatic process in CL of cyclic peroxides. In this article, the basic principle of TSH-MD and the successful applications on the CL reactions were shortly review.     

Quasi-Classical Trajectory Investigation of H+SO$ _{2} \rightarrow $OH+SO Reaction on Full-Dimensional Accurate Potential Energy Surface

The reaction H+SO\begin{document}$ _2 $\end{document}\begin{document}$ \rightarrow $\end{document}OH+SO is important in the combustion and atmospheric chemistry, as well as the interstellar medium. It also represents a typical complex-forming reaction with deep complexes, serving as an ideal candidate for testing various kinetics theories and providing interesting reaction dynamical phenomena. In this work, we reported a quasi-classical trajectory study of this reaction on our previously developed accurate full-dimensional potential energy surface. The experimental thermal rate coefficients over the temperature range 1400 K\begin{document}$ \leq $\end{document}\begin{document}$ T $\end{document}\begin{document}$ \leq $\end{document} 2200 K were well reproduced. For the reactant SO\begin{document}$ _2 $\end{document} being sampled at the ground ro-vibrational state, the calculated integral cross sections increased slightly along the collision energy ranging from 31.0 kcal/mol to 40.0 kcal/mol, and then became essentially flat at the collision energy within 40.0\begin{document}$ - $\end{document}55.0 kcal/mol. The product angular distributions are almost symmetric with nearly identical backward-forward double peak structure. The products OH and SO vibrational state distributions were also analyzed.     

Theoretical Study on the Long-lived Complexes for the Na＋I2 Collision System

For the Na I2 collision system, theoretical study is performed on the QCISD(T) level by using ab initio method. The ab initio potential energy surfaces are got and on them the long-lived complexes are found and optimized. These results verify the crossed molecule beam experimental phenomenon and the detailed geometry structures are given for the first time. The role of the complexes in the reaction path is also described in detail.     

Ultrafast Nonadiabatic Photoisomerization Dynamics Mechanism for the UV Photoprotection of Stilbenoids in Grape Skin

Natural UV photoprotection plays a vital role in physiological protection. It has been reported that UVC radiation can make resveratrol (RSV) and piceatannol (PIC) accumulate in grape skin. In this work, we demonstrated that RSV and PIC could significantly absorb UVA and UVB, and confirmed their satisfactory photostability. Furthermore, we clarified the UV photoprotection mechanism of typical stilbenoids of RSV and PIC for the first time by using combined femtosecond transient absorption (FTA) spectroscopy and time‐dependent density functional theory (TD‐DFT) calculations. RSV and PIC can be photoexcited to the excited state after UVA and UVB absorption. Subsequently, the photoisomerized RSV and PIC quickly relax to the ground state via nonadiabatic transition from the S₁ state at a conical intersection (CI) position between potential energy surfaces (PESs) of S₁ and S₀ states. This ultrafast trans‐cis photoisomerization will take place within a few tens of picoseconds. As a result, the UV energy absorbed by RSV and PIC could be dissipated by an ultrafast nonadiabatic photoisomerization process.