Full and
            <i>Ab Initio</i>
            Multiple Spawning

Curchod, Basile F. E.

doi:10.1002/9781119417774.ch14

Cited by 12 publications

(16 citation statements)

References 84 publications

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“…DD-vMCG is a frozen Gaussian nuclear dynamics method that shares the wavefunction ansatz with the full multiple spawning method of Curchod and Martínez [ 37 , 46 ] and the coupled coherent method of Shalashilin [ 47 ], but both these methods use classical trajectories to propagate the Gaussian centres, while in vMCG the Gaussian basis functions follow variationally determined trajectories to keep the basis set optimally small. The method has been describe extensively in the literature [ 48 , 49 , 50 ] and will only be outlined here.…”

Section: Methodsmentioning

confidence: 99%

“…Their 21 independent trajectories generated from a Wigner distribution (that increased to 186 due to the spawning) confirmed that the dimethyl torsion is not involved in the early S

transfer and that only the phenol C=C ring bonds showed sizeable variations during this short time. In a later publication, Ibele and Curchod pointed out that, during this fast transfer, different points of the intersection seam were visited and that one would expect a branching of the nuclear wavepacket without a posterior recombination [ 37 ].…”

Section: Introductionmentioning

confidence: 99%

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Micro-Solvated DMABN: Excited State Quantum Dynamics and Dual Fluorescence Spectra

2021

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In this work, we report a complete analysis by theoretical and spectroscopic methods of the short-time behaviour of 4-(dimethylamino)benzonitrile (DMABN) in the gas phase as well as in cyclohexane, tetrahydrofuran, acetonitrile, and water solution, after excitation to the La state. The spectroscopic properties of DMABN were investigated experimentally using UV absorption and fluorescence emission spectroscopy. The computational study was developed at different electronic structure levels and using the Polarisable Continuum Model (PCM) and explicit solvent molecules to reproduce the solvent environment. Additionally, excited state quantum dynamics simulations in the diabatic picture using the direct dynamics variational multiconfigurational Gaussian (DD-vMCG) method were performed, the largest quantum dynamics “on-the-fly” simulations performed with this method until now. The comparison with fully converged multilayer multiconfigurational time-dependent Hartree (ML-MCTDH) dynamics on parametrised linear vibronic coupling (LVC) potentials show very similar population decays and evolution of the nuclear wavepacket. The ring C=C stretching and three methyl tilting modes are identified as the responsible motions for the internal conversion from the La to the Lb states. No major differences are observed in the ultrafast initial decay in different solvents, but we show that this effect depends strongly on the level of electronic structure used.

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Section: Methodsmentioning

confidence: 99%

“…Their 21 independent trajectories generated from a Wigner distribution (that increased to 186 due to the spawning) confirmed that the dimethyl torsion is not involved in the early S

Section: Introductionmentioning

confidence: 99%

Micro-Solvated DMABN: Excited State Quantum Dynamics and Dual Fluorescence Spectra

2021

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“…An alternative is direct dynamics (dd) methods that expand the molecular wave function by classical or semiclassical trajectories. Examples include surface hopping (SH), ab initio multiple spawning (AIMS), ab initio multiconfigurational Ehrenfest (AIMCE), and direct dynamics variational multiconfigurational Gaussians (dd-vMCG). − In a general form, the direct dynamics wave function | Ψ dd false( t false) false⟩ can be expressed as, | Ψ dd false( t false) ⟩ = ∑ n = 1 N TBF c n false( t false) | ψ n ( t ) false⟩ with c n ( t ) the expansion coefficient for each of the N TBF trajectory basis functions (TBFs) given by, false| ψ n ( t ) false⟩ = ( ∑ k = 1 N s a k n ( t ) false| ψ k ⟩ ) false| χ n false( t false) ⟩ where the parentheses contains the electronic states |ψ k ⟩ and...…”

Section: Theorymentioning

confidence: 99%

Robust Inversion of Time-Resolved Data via Forward-Optimization in a Trajectory Basis

Acheson

Kirrander

2023

J. Chem. Theory Comput.

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An inversion method for time-resolved data from ultrafast experiments is introduced, based on forward-optimization in a trajectory basis. The method is applied to experimental data from X-ray scattering of the photochemical ring-opening reaction of 1,3-cyclohexadiene and electron diffraction of the photodissociation of CS2. In each case, inversion yields a model that reproduces the experimental data, identifies the main dynamic motifs, and agrees with independent experimental observations. Notably, the method explicitly accounts for continuity constraints and is robust even for noisy data.

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“…The spawning procedure follows the prescription of [46]. To avoid any numerical instability due to τss′,klfalse(tfalse) (see equations (2.10–2.11) and the subsequent discussion) in solving the equation of motion for the coefficients when trajectories pass close to the CI, we employ the Padé approximant to the exact solution of the Schrödinger equation so that the time-derivative in equation (2.10) does not appear.…”

Section: Computational Detailsmentioning

confidence: 99%

“…Then, we numerically expose the ability of the MCA representation to describe the exact dynamics well. We employ the Full Multiple Spawning approach to evolve the Gaussian basis functions [46] with classically evolving Gaussian centres [47].…”

Section: Introductionmentioning

confidence: 99%

The moving crude adiabatic alternative to the adiabatic representation in excited state dynamics

Maskri

Joubert-Doriol

2022

Phil. Trans. R. Soc. A.

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The choice of the electronic representation in on-the-fly quantum dynamics is crucial. The adiabatic representation is appealing since adiabatic states are readily available from quantum chemistry packages. The nuclear wavepackets are then expanded in a basis of Gaussian functions, which follow trajectories to explore the potential energy surfaces and approximate the potential using a local expansion of the adiabatic quantities. Nevertheless, the adiabatic representation is plagued with severe limitations when conical intersections are involved: the diagonal Born–Oppenheimer corrections (DBOCs) are non-integrable, and the geometric phase effect on the nuclear wavepackets cannot be accounted for unless a model is available. To circumvent these difficulties, the moving crude adiabatic (MCA) representation was proposed and successfully tested in low energy dynamics where the wavepacket skirts the conical intersection. We assess the MCA representation in the case of non-adiabatic transitions through conical intersections. First, we show that using a Gaussian basis in the adiabatic representation indeed exhibits the aforementioned difficulties with a special emphasis on the possibility to regularize the DBOC terms. Then, we show that MCA is indeed able to properly model non-adiabatic transitions. Tests are done on linear vibronic coupling models for the bis(methylene) adamantyl cation and the butatriene cation. This article is part of the theme issue ‘Chemistry without the Born–Oppenheimer approximation’.

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Full and Ab Initio Multiple Spawning

Cited by 12 publications

References 84 publications

Micro-Solvated DMABN: Excited State Quantum Dynamics and Dual Fluorescence Spectra

Micro-Solvated DMABN: Excited State Quantum Dynamics and Dual Fluorescence Spectra

Robust Inversion of Time-Resolved Data via Forward-Optimization in a Trajectory Basis

The moving crude adiabatic alternative to the adiabatic representation in excited state dynamics

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