Exploring dynamical electron theory beyond the Born–Oppenheimer framework: from chemical reactivity to non-adiabatically coupled electronic and nuclear wavepackets on-the-fly under laser field

Takatsuka, Kazuo; Yonehara, Takehiro

doi:10.1039/c0cp00937g

Cited by 70 publications

(61 citation statements)

References 112 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…where the lead article of Tully provides a useful summary of the state of the art. 16 There have been two recent reviews, which include a comprehensive discourse on the Ehrenfest method, 43, 44 so we will be content with a few general statements. In the Ehrenfest approach, the nuclear motion is described by classical mechanics following a trajectory Q(t), while the electronic motion is described quantum mechanically by a timedependent wavefunction (t), satisfying the time-dependent Schrödinger equation in atomic units…”

Section: A Ehrenfest Methodsmentioning

confidence: 99%

Coupled electron-nuclear dynamics: Charge migration and charge transfer initiated near a conical intersection

Mendive-Tapia

Vacher

Bearpark

et al. 2013

The Journal of Chemical Physics

View full text Add to dashboard Cite

Coupled electron-nuclear dynamics, implemented using the Ehrenfest method, has been used to study charge migration with fixed nuclei, together with charge transfer when nuclei are allowed to move. Simulations were initiated at reference geometries of neutral benzene and 2-phenylethylamine (PEA), and at geometries close to potential energy surface crossings in the cations. Cationic eigenstates, and the so-called sudden approximation, involving removal of an electron from a correlated ground-state wavefunction for the neutral species, were used as initial conditions. Charge migration without coupled nuclear motion could be observed if the Ehrenfest simulation, using the sudden approximation, was started near a conical intersection where the states were both strongly coupled and quasi-degenerate. Further, the main features associated with charge migration were still recognizable when the nuclear motion was allowed to couple. In the benzene radical cation, starting from the reference neutral geometry with the sudden approximation, one could observe sub-femtosecond charge migration with a small amplitude, which results from weak interaction with higher electronic states. However, we were able to engineer large amplitude charge migration, with a period between 10 and 100 fs, corresponding to oscillation of the electronic structure between the quinoid and anti-quinoid cationic electronic configurations, by distorting the geometry along the derivative coupling vector from the D 6h Jahn-Teller crossing to lower symmetry where the states are not degenerate. When the nuclear motion becomes coupled, the period changes only slightly. In PEA, in an Ehrenfest trajectory starting from the D 2 eigenstate and reference geometry, a partial charge transfer occurs after about 12 fs near the first crossing between D 1 , D 2 (N + -Phenyl, N-Phenyl + ). If the Ehrenfest propagation is started near this point, using the sudden approximation without coupled nuclear motion, one observes an oscillation of the spin density -charge migration -between the N atom and the phenyl ring with a period of 4 fs. When the nuclear motion becomes coupled, this oscillation persists in a damped form, followed by an effective charge transfer after 30 fs. © 2013 AIP Publishing LLC.

show abstract

Section: A Ehrenfest Methodsmentioning

confidence: 99%

Coupled electron-nuclear dynamics: Charge migration and charge transfer initiated near a conical intersection

Mendive-Tapia

Vacher

Bearpark

et al. 2013

The Journal of Chemical Physics

View full text Add to dashboard Cite

show abstract

“…The Ehrenfest method has been extensively discussed in the literature [16][17][18][19][20][21][22][23][24][25][26]. In this section, we review the Ehrenfest formalism following the elegant derivation of Tully [27].…”

Section: The Ehrenfest Approach: General Theoretical Developmentmentioning

confidence: 99%

The second-order Ehrenfest method

et al. 2014

View full text Add to dashboard Cite

This article describes the Ehrenfest method and our second-order implementation (with approximate gradient and Hessian) within a CASSCF formalism. We demonstrate that the second order implementation with the predictor-corrector integration method improves the accuracy of the simulation significantly in terms of energy conservation. Although the method is general and can be used to study any coupled electron-nuclear dynamics, we apply it to investigate charge migration upon ionization of small organic molecules, focusing on benzene cation. Using this approach, we can study the evolution of a non-stationary electronic wavefunction for fixed atomic nuclei, and where the nuclei are allowed to move, to investigate the interplay between them for the first time. Analysis methods for the interpretation of the electronic and nuclear dynamics are suggested: we monitor the electronic dynamics by calculating the spin density of the system as a function of time.

show abstract

“…2,3,[39][40][41][42][43][44][45][46][47] In this theoretical framework, a Hamiltonian in the general mixed quantum and classical representation described in the electronic Hilbert space and nuclear configuration space is first established, with which the electronic wavepacket dynamics as well as the relevant nuclear path solutions are sought for. The solutions of these dynamics give rise to infinitely many branching nuclear paths to represent the wavepacket bifurcation as emphasized above.…”

Section: Introductionmentioning

confidence: 99%

Electronic quantum effects mapped onto non-Born-Oppenheimer nuclear paths: Nonclassical surmounting over potential barriers and trapping above the transition states due to nonadiabatic path-branching

Yamamoto

Takatsuka

2014

The Journal of Chemical Physics

Self Cite

View full text Add to dashboard Cite

We develop the path-branching representation for nonadiabatic electron wavepacket dynamics [T. Yonehara and K. Takatsuka, J. Chem. Phys. 132, 244102 (2010)] so as to treat dynamics in an energy range comparable to the barrier height of adiabatic potential energy curves. With this representation two characteristic chemical reaction dynamics are studied, in which an incident nuclear wavepacket encounters a potential barrier, on top of which lies another nonadiabatically coupled adiabatic potential curve: (1) Dynamics of initial paths coming into the nonadiabatic interaction region with energy lower than the barrier height. They branch into two pieces (and repeat branching subsequently), the upper counterparts of which can penetrate into a classically inaccessible high energy region and eventually branch back to the product region on the ground state curve. This is so to say surmounting the potential barrier via nonadiabatically coupled excited state, and phenomenologically looks like the so-called deep tunneling. (2) Dynamics of classical paths whose initial energies are a little higher than the barrier but may be lower than the bottom of the excited state. They can undergo branching and some of those components are trapped on top of the potential barrier, being followed by the population decay down to the lower state flowing both to product and reactant sites. Such expectations arising from the path-branching representation are numerically confirmed with full quantum mechanical wavepacket dynamics. This phenomenon may be experimentally observed as time-delayed pulses of wavepacket trains.

show abstract

Exploring dynamical electron theory beyond the Born–Oppenheimer framework: from chemical reactivity to non-adiabatically coupled electronic and nuclear wavepackets on-the-fly under laser field

Cited by 70 publications

References 112 publications

Coupled electron-nuclear dynamics: Charge migration and charge transfer initiated near a conical intersection

Coupled electron-nuclear dynamics: Charge migration and charge transfer initiated near a conical intersection

The second-order Ehrenfest method

Electronic quantum effects mapped onto non-Born-Oppenheimer nuclear paths: Nonclassical surmounting over potential barriers and trapping above the transition states due to nonadiabatic path-branching

Contact Info

Product

Resources

About