The Classical Trajectory‐Surface‐Hopping Approach to Charge‐Transfer Processes

Chapman, Sally

doi:10.1002/9780470141403.ch7

Cited by 68 publications

(25 citation statements)

References 128 publications

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“…Many electronically nonadiabatic processes occur on time scales of femtoseconds to picoseconds, − and they are often faster than intramolecular vibrational relaxation; hence they must be treated nonstatistically. Electronically nonadiabatic molecular dynamics is required for this purpose, − and we are concerned here with methods employing mixed quantum–classical dynamics, which in the present article refers to algorithms in which the electrons are treated quantum mechanically and the nuclei are treated classically or semiclassically. In such methods, the nuclei propagate on an effective potential, which may be a self-consistent potential, as in the semiclassical Ehrenfest method − or the coherent switches with decay of mixing (CSDM) method, or it may be an unaveraged adiabatic or diabatic PES; in the unaveraged case the dynamics is punctuated by switches to other PESs, as in the trajectory surface hopping (TSH) method. − , The use of a self-consistent potential is particularly appropriate in regions with closely coupled electronic states, e.g., in a region near a conical intersection seam, where propagation on a single potential energy surface is not justified by the Born–Oppenheimer approximation.…”

Section: Introductionmentioning

confidence: 99%

“…In such methods, the nuclei propagate on an effective potential, which may be a self-consistent potential, as in the semiclassical Ehrenfest method 31−33 or the coherent switches with decay of mixing (CSDM) method, 34 or it may be an unaveraged adiabatic or diabatic PES; in the unaveraged case the dynamics is punctuated by switches to other PESs, as in the trajectory surface hopping (TSH) method. [13][14][15][16]21 The use of a self-consistent potential is particularly appropriate in regions with closely coupled electronic states, e.g., in a region near a conical intersection seam, where propagation on a single potential energy surface is not justified by the Born− Oppenheimer approximation. Most electronically nonadiabatic processes are controlled by such regions.…”

Section: Introductionmentioning

confidence: 99%

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Implementation of Coherent Switching with Decay of Mixing into the SHARC Program

Shu

Zhang

Mai

et al. 2020

J. Chem. Theory Comput.

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Simulation of electronically nonadiabatic dynamics is an important tool for understanding the mechanisms of photochemical and photophysical processes. Two contrasting methods in which the electrons are treated quantum mechanically while the nuclei are treated classically are semiclassical Ehrenfest dynamics and trajectory surface hopping; neither method in its original form includes decoherence. Decoherence in the context of electronically nonadiabatic dynamics refers to the gradual collapse of a coherent quantum mechanical electronic state under the scrutiny of nuclear motion into a mixture of stable pointer states. This is modeled in the coherent switches with decay of mixing (CSDM) method by the decay of the off-diagonal elements of the electronic density matrix. Here, we present an implementation of CSDM in the SHARC program; a key element of the new implementation is the use of a different propagator than that used previously in the ANT program.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Implementation of Coherent Switching with Decay of Mixing into the SHARC Program

Shu

Zhang

Mai

et al. 2020

J. Chem. Theory Comput.

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“…A popular semiclassical method is trajectory surface hopping (TSH). 1,2,9,33,34,35,36,37,38 In TSH one only requires the NAC in the direction of the current velocity, 𝐑 ̇, because the semiclassical equations only require the time derivative coupling (TDC):…”

Section: Introductionmentioning

confidence: 99%

Nonadiabatic Dynamics Algorithms with Only Potential Energies and Gradients: Curvature-Driven Coherent Switching with Decay of Mixing and Curvature-Driven Trajectory Surface Hopping

Shu

Zhang

Sun

et al. 2021

Preprint

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Direct dynamics by mixed quantum–classical nonadiabatic methods is an important tool for understanding processes involving multiple electronic states. Very often, the computational bottleneck of such direct simulation comes from electronic structure theory. For example, at every time step of a trajectory, nonadiabatic dynamics requires potential energy surfaces, their gradients, and the matrix elements coupling the surfaces. The need for the couplings can be alleviated by employing the time derivatives of the wave functions, which can be evaluated from overlaps of electronic wave functions at successive timesteps. However, evaluation of overlap integrals is still expensive for large systems. In addition, for electronic structure methods for which the wave functions or the coupling matrix elements are not available, nonadiabatic dynamics algorithms become inapplicable. In this work, building on recent work by Baeck and An, we propose new nonadiabatic dynamics algorithms that only require adiabatic potential energies and their gradients. The new methods are named curvature- driven coherent switching with decay of mixing (κCSDM) and curvature-driven trajectory surface hopping (κTSH). We show how powerful these new methods are in terms of computer time and good agreement with methods employing nonadiabatic coupling vectors computed in conventional ways. The lowering of the computational cost will allow longer nonadiabatic trajectories and greater ensemble averaging to be affordable, and the ability to calculate the dynamics without electronic structure coupling matrix elements extends the dynamics capability to new classes of electronic structure methods.

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“…According to this philosophy, current methodology developments for studying reaction dynamics in more complex systems can be roughly divided into two major classes, approximate and numerically exact. Approaches in the first category include, for example, mixed quantum-classical − and semiclassical approaches. − The advantages of these approximate methods are their generality and ease of application. In principle, they can be used to treat any form of analytic potential functions or even ab initio potential energy surfaces generated on the fly.…”

Section: Introductionmentioning

confidence: 99%

Multilayer Multiconfiguration Time-Dependent Hartree Theory

2015

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Multilayer multiconfiguration time-dependent Hartree (ML-MCTDH) theory is a rigorous and powerful method to simulate quantum dynamics in complex many-body systems. This approach extends the original MCTDH theory of Meyer, Manthe, and Cederbaum to include dynamically contracted layers in a recursive way, within which the equations of motion are determined from the Dirac-Frenkel variational principle. This paper presents the general derivation of the theory and analyzes the important features that make the ML-MCTDH method numerically efficient. Furthermore, we discuss the generalization of the theory to treat many-body identical particles (fermions or bosons) as well as calculating energy eigenstates via the improved relaxation method.

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The Classical Trajectory‐Surface‐Hopping Approach to Charge‐Transfer Processes

Cited by 68 publications

References 128 publications

Implementation of Coherent Switching with Decay of Mixing into the SHARC Program

Implementation of Coherent Switching with Decay of Mixing into the SHARC Program

Nonadiabatic Dynamics Algorithms with Only Potential Energies and Gradients: Curvature-Driven Coherent Switching with Decay of Mixing and Curvature-Driven Trajectory Surface Hopping

Multilayer Multiconfiguration Time-Dependent Hartree Theory

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