Generalized Ab Initio Nonadiabatic Dynamics Simulation Methods from Molecular to Extended Systems

Abstract

Nonadiabatic dynamics simulation has become a powerful tool to describe nonadiabatic effects involved in photophysical processes and photochemical reactions. In the past decade, our group has developed generalized trajectory-based ab initio surface-hopping (GTSH) dynamics simulation methods, which can be used to describe a series of nonadiabatic processes, such as internal conversion, intersystem crossing, excitation energy transfer and charge transfer of molecular systems, and photoinduced nonadiabatic carrier dynamics of extended systems with and without spin–orbit couplings. In this contribution, we will first give a brief introduction to our recently developed methods and related numerical implementations at different computational levels. Later, we will present some of our latest applications in realistic systems, which cover organic molecules, biological proteins, organometallic compounds, periodic organic and inorganic materials, etc. Final discussion is given to challenges and outlooks of ab initio nonadiabatic dynamics simulations.

Understanding the Excited-State Relaxation Mechanisms of Xanthophyll Lutein by Multi-configurational Electronic Structure Calculations

“…It is well-known that the DFT method can give a reasonable description of geometric structures in the ground state at a relatively low computational cost. , Therefore, the ground-state minimum structures of lutein, labeled as S 0 (1Ag – ), were first optimized with B3LYP functionals with 6-31G* and 6-31G ** basis sets. In addition, the cheaper semiempirical OM2/MRCI­(20,20) method (see Figure ) and the more expensive multi-configurational CASSCF and RASSCF methods with different basis sets were also performed to locate the same ground-state minimum structure.…”

Nonadiabatic Dynamics Simulations for Photoinduced Processes in Molecules and Semiconductors: Methodologies and Applications

“…This method has been implemented in our own GTSH package and widely used to simulation photoinduced ultrafast processes of molecular, biological, and material systems. 66 In addition, the overcoherence problem existing in many MQC-based NAMD methods, including the widely used EMF, TSH algorithms, can lead to problematic results if not being treated properly. 167−169 Therefore, the decoherence correction is necessary during the propagation of the trajectories.…”

“…Nowadays, the number of studies focused on the evaluation of photoinduced carrier dynamics, including electron/hole transfer (PET/PHT) and separation (CS), charge recombination (CR), and hot carrier relaxation (HCR) has surged (Figure b). Experimentalists usually employ time-resolved spectroscopic techniques to investigate the dynamics upon photoexcitation and many insightful results have been obtained. ,− ,− ,− ,, Theoretically, it is very useful to seek the help of nonadiabatic dynamics (NAMD) simulations for an in-depth understanding of the microscopic mechanism of these photoexcited systems. ,− From a microscopic point of view, the basic building blocks of a photofunctional materials are vastly different, according to which different simulation strategies can be adopted to efficiently investigate their photoinduced properties. For instance, since the basic components of molecular crystals and organic polymers are molecules or polymers, the corresponding photoinduced dynamics can be deduced by exploring the photoinduced dynamics of the constituent molecules. − These kind of systems can therefore be called molecular systems from a theoretical point of view.…”

New Gradient Correction Scheme for Electronically Nonadiabatic Dynamics Involving Multiple Spin States

“…Semiclassical dynamics is widely used to investigate electronically nonadiabatic processes, i.e., processes in which electronic excitation energy is converted to internuclear vibrations, or vice versa. − Intersystem crossing is promoted in the vicinity of crossings between potential energy surfaces corresponding to different spin states, − in contrast to internal conversion, which is promoted near the crossings (called conical intersections) of same-spin states. − The present article is concerned with intersystem crossing. We are especially interested in direct nonadiabatic dynamics simulations, which can be a powerful tool for understanding the mechanism of intersystem crossing. ,− …”