Molecular dynamics with electronic transitions

Tully, John C.

doi:10.1063/1.459170

Cited by 3,439 publications

(4,210 citation statements)

References 52 publications

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“…The solution may be represented in the form of an electronic density matrix q, where the diagonal element r ii is the electronic state probability for state i, and r ij for i 6 ¼ j are the electronic state coherences. 21,107 If the entire system is described in quantum mechanical language, then q is the reduced density matrix obtained by tracing the density matrix of the entire system (electrons and nuclei) over the nuclear degrees of freedom. The Schrö dinger equation for the wave function reduces (neglecting T ð2Þ ij ) to the following equation for the reduced density matrix: 85…”

Section: Semiclassical Trajectory Methodsmentioning

confidence: 99%

“…Note that the diagonal elements V ii can be qualitatively different in the adiabatic and diabatic representations, and therefore surface hopping methods are often very sensitive to the choice of electronic representation. The surface hopping method that has the most elegant derivation is the molecular dynamics with quantum transitions method of Tully; 21,107 we call this Tully's fewest-switches (TFS) method. Trajectories are propagated locally under the influence of a single-state potential energy function, and this propagation is interrupted at small time intervals with hopping decisions.…”

Section: Semiclassical Trajectory Methodsmentioning

confidence: 99%

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Introductory lecture: Nonadiabatic effects in chemical dynamics

et al. 2004

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Recent progress in the theoretical treatment of electronically nonadiabatic processes is discussed. First we discuss the generalized Born-Oppenheimer approximation, which identifies a subset of strongly coupled states, and the relative advantages and disadvantages of adiabatic and diabatic representations of the coupled surfaces and their interactions are considered. Ab initio diabatic representations that do not require tracking geometric phases or calculating singular nonadiabatic nuclear momentum coupling will be presented as one promising approach for characterizing the coupled electronic states of polyatomic photochemical systems. Such representations can be accomplished by methods based on functionals of the adiabatic electronic density matrix and the identification of reference orbitals for use in an overlap criterion. Next, four approaches to calculating or modeling electronically nonadiabatic dynamics are discussed: (1) accurate quantum mechanical scattering calculations, (2) approximate wave packet methods, (3) surface hopping, and (4) self-consistent-potential semiclassical approaches. The last two of these are particularly useful for polyatomic photochemistry, and recent refinements of these approaches will be discussed. For example, considerable progress has been achieved in making the surface hopping method more applicable to the study of systems with weakly coupled electronic states. This includes introducing uncertainty principle considerations to alleviate the problem of classically forbidden surface hops and the development of an efficient sampling algorithm for low-probability events. A topic whose central importance in a number of quantum mechanical fields is becoming more widely appreciated is the introduction of decoherence into the quantal degrees of freedom to account for the effect of the classical treatment on the other degrees of freedom, and we discuss how the introduction of such decoherence into a self-consistent-potential approximation leads to a reasonably accurate but very practical trajectory method for electronically nonadiabatic processes. Finally, the performances of several dynamical methods for Landau-Zener-type and Rosen-Zener-Demkov-type reactive scattering problems are compared.

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Section: Semiclassical Trajectory Methodsmentioning

confidence: 99%

Section: Semiclassical Trajectory Methodsmentioning

confidence: 99%

Introductory lecture: Nonadiabatic effects in chemical dynamics

et al. 2004

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“…51 The accuracy of SA-CASSCF potential energies is examined prior to the dynamical simulations by comparing with the MS-CASPT2 results. The gradients and nonadiabatic coupling vectors are evaluated analytically during the course of simulations.…”

Section: Computational Detailsmentioning

confidence: 99%

Photophysics of cytosine tautomers: new insights into the nonradiative decay mechanisms from MS-CASPT2 potential energy calculations and excited-state molecular dynamics simulations

Nakayama

Harabuchi

Yamazaki

et al. 2013

Phys. Chem. Chem. Phys.

111

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A comprehensive picture of the ultrafast nonradiative decay mechanisms of three cytosine tautomers (amino-keto, imino-keto, and amino-enol forms) is revealed by high-level ab initio potential energy calculations using the multistate (MS) CASPT2 method and also by on-the-fly excited-state molecular dynamics simulations employing the CASSCF method. To obtain a reliable potential energy profile along the deactivation pathways, the MS-CASPT2 method is employed even for the optimization of minimum energy structures in the excited state and conical intersection (CI) structures between the ground and excited states. In the imino (imino-keto) form, we locate a new CI structure involving the twisting of the imino group, and the decay pathway leading to this CI is found to be barrierless, suggesting a remarkably efficient deactivation of imino cytosine. In the keto (amino-keto) form, the MS-CASPT2 calculations exhibit an efficient decay path to the ethylene-like CI involving the twisting of C-C double bond in the six-membered ring, with a barrier of ~0.08 eV from the minimum of the 1 ππ* state. In the enol (amino-enol) form, three types of CIs are identified for the first time. Among them, the ethylene-like CI with a similar molecular structure to the keto form provides the most preferred deactivation pathway of enol cytosine. This pathway exhibits a higher barrier of ~0.22 eV and a higher energy of CI than those of keto cytosine. Nonadiabatic molecular dynamics simulations provide a time-dependent picture of the deactivation processes, including the excited-state lifetime of each tautomer. In particular, the decay time of the imino tautomer is predicted to be only ~100 fs. Our computational results are in remarkably good agreement with the experimental findings in recent femtosecond pump-probe photoionization spectroscopy [J. Am. Chem. Soc. 131, 16939 (2009); J. Phys. Chem. A 115, 8406 (2011)], supporting the coexistence of more than one tautomer in the photophysics of isolated cytosine and that each tautomer exhibits a different excited-state lifetime.1

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“…77 When the energy between two states reaches a certain limit (40 kcal mol −1 in our case), the MD step size is reduced (typically from 0.5 fs to 0.25 fs) and non-adiabatic coupling matrix elements are computed. The probabilities for remaining in the current 78,79 The time-dependent electronic wavefunction between the last and the actual MD step is therefore propagated (using a step ca. 100-200 times smaller than the actual MD step) under the assumption that inter-state coupling terms change linearly during this interval.…”

Section: Qm/mm Surface Hopping Dynamicsmentioning

confidence: 99%

Tracking the primary photoconversion events in rhodopsins by ultrafast optical spectroscopy

Polli

Rivalta

Nenov

et al. 2015

Photochem Photobiol Sci

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Opsins are a broad class of photoactive proteins, found in all classes of living beings from bacteria to higher animals, which work either as light-driven ion pumps or as visual pigments. The photoactive function in opsins is triggered by the ultrafast isomerization of the retinal chromophore around a specific carbon double bond, leading to a highly distorted, spectrally red-shifted photoproduct. Understanding, by either experimental or computational methods, the time course of this photoisomerization process is of utmost importance, both for its biological significance and because opsin proteins are the blueprint for molecular photoswitches. This paper focuses on the ultrafast 11-cis to all-trans isomerization in visual rhodopsins, and has a twofold goal: (i) to review the most recent experimental and computational efforts aimed at exposing the very early phases of photoconversion; and (ii) discuss future advanced experiments and calculations that will allow an even deeper understanding of the process. We present high time resolution pump-probe data, enabling us to follow the wavepacket motion through the conical intersection connecting excited and ground states, as well as femtosecond stimulated Raman scattering data allowing us to track the subsequent structural evolution until the first stable all-trans photoproduct is reached. We conclude by introducing computational results for two-dimensional electronic spectroscopy, which has the potential to provide even greater detail on the evolution of the electronic structure of retinal during the photoisomerization process.

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Molecular dynamics with electronic transitions

Cited by 3,439 publications

References 52 publications

Introductory lecture: Nonadiabatic effects in chemical dynamics

Introductory lecture: Nonadiabatic effects in chemical dynamics

Photophysics of cytosine tautomers: new insights into the nonradiative decay mechanisms from MS-CASPT2 potential energy calculations and excited-state molecular dynamics simulations

Tracking the primary photoconversion events in rhodopsins by ultrafast optical spectroscopy

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