Efficient first-principles electronic dynamics

Liang, Wenkel; Chapman, Craig T.; Li, Xiaosong

doi:10.1063/1.3589144

Cited by 67 publications

(63 citation statements)

References 42 publications

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“…Migration of the electron to a reactive site, which is a nonadiabatic process, can be difficult to characterize using Hartree-Fock self-consistent field computational methods or linear response methods, such as time-dependent density functional theory (TD-DFT) [36]. Advances in computational power and algorithm improvements have made it possible to perform Ehrenfest direct dynamics calculations [37][38][39] on systems of experimental interest. Ehrenfest dynamics allows us to follow the ab initio, non-adiabatic trajectory of systems on a mean potential energy surface (PES) within a coherent electronic wave function framework.…”

Section: Introductionmentioning

confidence: 99%

The Early Life of a Peptide Cation-Radical. Ground and Excited-State Trajectories of Electron-Based Peptide Dissociations During the First 330 Femtoseconds

Moss

Liang

et al. 2011

J. Am. Soc. Mass Spectrom.

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We report a new approach to investigating the mechanisms of fast peptide cation-radical dissociations based on an analysis of time-resolved reaction progress by Ehrenfest dynamics, as applied to an Ala-Arg cation-radical model system. Calculations of stationary points on the ground electronic state that were carried out with effective CCSD(T)/6-311++G(3df,2p) could not explain the experimental branching ratios for loss of a hydrogen atom, ammonia, and N-C(α) bond dissociation in (AR + 2H)(+•). The Ehrenfest dynamics results indicate that the ground and low-lying excited electronic states of (AR + 2H)(+•) follow different reaction courses in the first 330 femtoseconds after electron attachment. The ground (X) state undergoes competing loss of N-terminal ammonia and isomerization to an aminoketyl radical intermediate that depend on the vibrational energy of the charge-reduced ion. The A and B excited states involve electron capture in the Arg guanidine and carboxyl groups and are non-reactive on the short time scale. The C state is dissociative and progresses to a fast loss of an H atom from the Arg guanidine group. Analogous results were obtained by using the B3LYP and CAM-B3LYP density functionals for the excited state dynamics and including the universal M06-2X functional for ground electronic state calculations. The results of this Ehrenfest dynamics study indicate that reaction pathway branching into the various dissociation channels occurs in the early stages of electron attachment and is primarily determined by the electronic states being accessed. This represents a new paradigm for the discussion of peptide dissociations in electron based methods of mass spectrometry.

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Section: Introductionmentioning

confidence: 99%

The Early Life of a Peptide Cation-Radical. Ground and Excited-State Trajectories of Electron-Based Peptide Dissociations During the First 330 Femtoseconds

Moss

Liang

et al. 2011

J. Am. Soc. Mass Spectrom.

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“…The computational simulation of photodynamical processes involving radiationless transitions between multiple excited states in polyatomic molecules is one of the main goals in the field of molecular organic photochemistry. [1][2][3][4][5] In the last decade, direct nonadiabatic molecular dynamics (NA-MD) simulations [6][7][8] have been playing an important role in the study of photochemical and photophysical deactivation mechanisms in organic compounds. [9][10][11][12][13] Furthermore, ab initio NA-MD have been successfully applied to study ultrafast photoinduced electron transfer (ET) processes 14,15 in quantum dots, 16,17 and Auger phenomena including multiple exciton generation and recombination.…”

Section: Introductionmentioning

confidence: 99%

Identification of unavoided crossings in nonadiabatic photoexcited dynamics involving multiple electronic states in polyatomic conjugated molecules

Fernández-Alberti¹,

Roitberg²,

Nelson³

et al. 2012

The Journal of Chemical Physics

201

310

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Radiationless transitions between electronic excited states in polyatomic molecules take place through unavoided crossings of the potential energy surfaces with substantial non-adiabatic coupling between the respective adiabatic states. While the extent in time of these couplings are large enough, these transitions can be reasonably well simulated through quantum transitions using trajectory surface hopping-like methods. In addition, complex molecular systems may have multiple "trivial" unavoided crossings between noninteracting states. In these cases, the non-adiabatic couplings are described as sharp peaks strongly localized in time. Therefore, their modeling is commonly subjected to the identification of regions close to the particular instantaneous nuclear configurations for which the energy surfaces actually cross each other. Here, we present a novel procedure to identify and treat these regions of unavoided crossings between non-interacting states using the so-called Min-Cost algorithm. The method differentiates between unavoided crossings between interacting states (simulated by quantum hops), and trivial unavoided crossings between non-interacting states (detected by tracking the states in time with Min-Cost procedure). We discuss its implementation within our recently developed non-adiabatic excited state molecular dynamics framework. Fragments of two- and four-ring linear polyphenylene ethynylene chromophore units at various separations have been used as a representative molecular system to test the algorithm. Our results enable us to distinguish and analyze the main features of these different types of radiationless transitions the molecular system undertakes during internal conversion.

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“…In this article we study B-DNA monomers and dimers with RT-TDDFT, which is one of the few computationally viable techniques to model carrier dynamics in molecular systems [21][22][23][24]. RT-TDDFT can simulate density fluctuations of the order of attoseconds to femtoseconds and can model the effects of an ultrafast, intense, short-pulse laser field, including the full (nonlinear) response of the electron density [25].…”

Section: Introductionmentioning

confidence: 99%

RT-TDDFT study of hole oscillations in B-DNA monomers and dimers

et al. 2017

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We employ Real-Time Time-Dependent Density Functional Theory to study hole oscillations within a B-DNA monomer (one base pair) or dimer (two base pairs). Placing the hole initially at any of the bases which make up a base pair, results in THz oscillations, albeit of negligible amplitude. Placing the hole initially at any of the base pairs which make up a dimer is more interesting: For dimers made of identical monomers, we predict oscillations with frequencies in the range f ≈ 20-80 THz, with a maximum transfer percentage close to 1. For dimers made of different monomers, f ≈ 80-400 THz, but with very small or small maximum transfer percentage. We compare our results with those obtained recently via our Tight-Binding approaches and find that they are in good agreement.

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Efficient first-principles electronic dynamics

Cited by 67 publications

References 42 publications

The Early Life of a Peptide Cation-Radical. Ground and Excited-State Trajectories of Electron-Based Peptide Dissociations During the First 330 Femtoseconds

The Early Life of a Peptide Cation-Radical. Ground and Excited-State Trajectories of Electron-Based Peptide Dissociations During the First 330 Femtoseconds

Identification of unavoided crossings in nonadiabatic photoexcited dynamics involving multiple electronic states in polyatomic conjugated molecules

RT-TDDFT study of hole oscillations in B-DNA monomers and dimers

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