Acceleration of self‐consistent field convergence in <i>ab initio</i> molecular dynamics simulation with multiconfigurational wave function

Okoshi, Masaki; Nakai, Hiromi

doi:10.1002/jcc.23617

Cited by 2 publications

(1 citation statement)

References 28 publications

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“…Despite the status of DMABN as the archetypal dual fluorescence system, and the considerable amount of theoretical attention it has received, there are only relatively few reports of computer simulations of its excited-state relaxation dynamics. Some such studies − focused on the solvation of the photoexcited DMABN molecule, and others , used simplified models of the molecule as test cases for the development of simulation methods. In order to improve the theoretical understanding of this important system by providing information that cannot be obtained from static calculations alone, and may be directly compared to experimental measurements, such as the sequence and time scale of events, we have carried out dynamical (which is to say, time-resolved) simulations of the gas-phase relaxation mechanism.…”

Section: Introductionmentioning

confidence: 99%

Early Events in the Nonadiabatic Relaxation Dynamics of 4-(N,N-Dimethylamino)benzonitrile

Kochman

Tajti

Morrison

et al. 2015

J. Chem. Theory Comput.

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4-(N,N-Dimethylamino)benzonitrile (DMABN) is the archetypal system for dual fluorescence. Several past studies, both experimental and theoretical, have examined the mechanism of its relaxation in the gas phase following photoexcitation to the S2 state, without converging to a single description. In this contribution, we report first-principles simulations of the early events involved in this process performed using the nonadiabatic trajectory surface hopping (TSH) approach in combination with the ADC(2) electronic structure method. ADC(2) is verified to reproduce the ground- and excited-state structures of DMABN in reasonably close agreement with previous theoretical benchmarks. The TSH simulations predict that internal conversion from the S2 state to the S1 takes place as early as 8.5 fs, on average, after the initial photoexcitation, and with no significant torsion of the dimethylamino group relative to the aromatic ring. As evidenced by supporting EOM-CCSD calculations, the population transfer from S2 to S1 can be attributed to the skeletal deformation modes of the aromatic ring and the stretching of the ring-dimethylamino nitrogen bond. The non- or slightly twisted locally excited structure is the predominant product of the internal conversion, and the twisted intramolecular charge transfer structure is formed through equilibration with the locally excited structure with no change of adiabatic state. These findings point toward a new interpretation of data from previous time-resolved experiments.

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Section: Introductionmentioning

confidence: 99%

Early Events in the Nonadiabatic Relaxation Dynamics of 4-(N,N-Dimethylamino)benzonitrile

Kochman

Tajti

Morrison

et al. 2015

J. Chem. Theory Comput.

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The transition from the open minimum to the ring minimum on the ground state and on the lowest excited state of like symmetry in ozone: A configuration interaction study

Theis

Ivanic

Windus

et al. 2016

The Journal of Chemical Physics

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The metastable ring structure of the ozone 1 1 A 1 ground state, which theoretical calculations have shown to exist, has so far eluded experimental detection. An accurate prediction for the energy difference between this isomer and the lower open structure is therefore of interest, as is a prediction for the isomerization barrier between them, which results from interactions between the lowest two 1 A 1 states. In the present work, valence correlated energies of the 1 1 A 1 state and the 2 1 A 1 state were calculated at the 1 1 A 1 open minimum, the 1 1 A 1 ring minimum, the transition state between these two minima, the minimum of the 2 1 A 1 state, and the conical intersection between the two states. The geometries were determined at the full-valence multi-configuration self-consistent-field level. Configuration interaction (CI) expansions up to quadruple excitations were calculated with triple-zeta atomic basis sets. The CI expansions based on eight different reference configuration spaces were explored. To obtain some of the quadruple excitation energies, the method of Correlation Energy Extrapolation by Intrinsic Scaling was generalized to the simultaneous extrapolation for two states. This extrapolation method was shown to be very accurate. On the other hand, none of the CI expansions were found to have converged to millihartree (mh) accuracy at the quadruple excitation level. The data suggest that convergence to mh accuracy is probably attained at the sextuple excitation level. On the 1 1 A 1 state, the present calculations yield the estimates of (ring minimum-open minimum) ∼45-50 mh and (transition state-open minimum) ∼85-90 mh. For the (2 1 A 1 -1 A 1 ) excitation energy, the estimate of ∼130-170 mh is found at the open minimum and 270-310 mh at the ring minimum. At the transition state, the difference (2 1 A 1 -1 A 1 ) is found to be between 1 and 10 mh. The geometry of the transition state on the 1 1 A 1 surface and that of the minimum on the 2 1 A 1 surface nearly coincide. More accurate predictions of the energy differences also require CI expansions to at least sextuple excitations with respect to the valence space. For every wave function considered, the omission of the correlations of the 2s oxygen orbitals, which is a widely used approximation, was found to cause errors of about ±10 mh with respect to the energy differences. C 2016 AIP Publishing LLC. [http://dx

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Acceleration of self‐consistent field convergence in ab initio molecular dynamics simulation with multiconfigurational wave function

Cited by 2 publications

References 28 publications

Early Events in the Nonadiabatic Relaxation Dynamics of 4-(N,N-Dimethylamino)benzonitrile

Early Events in the Nonadiabatic Relaxation Dynamics of 4-(N,N-Dimethylamino)benzonitrile

The transition from the open minimum to the ring minimum on the ground state and on the lowest excited state of like symmetry in ozone: A configuration interaction study

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