Intramolecular vibrational energy redistribution in toluene: a nine-dimensional quantum mechanical study using the MCTDH algorithm

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We report energies and tunneling splittings of vibrational excited states of malonaldehyde which have been obtained using full dimensional quantum mechanical calculations. To this end we employed the multi configuration time-dependent Hartree method. The results have been obtained using a recently published potential energy surface [Y. Wang, B. J. Braams, J. M. Bowman, S. Carter, and D. P. Tew, J. Chem. Phys. 128, 224314 (2008)] which has been brought into a suitable form by a modified version of the n-mode representation which was used with two different arrangements of coordinates. The relevant terms of the expansion have been identified with a Metropolis algorithm and a diffusion Monte-Carlo technique, respectively.

Section: Improved Relaxationmentioning

confidence: 99%

Calculation of the vibrational excited states of malonaldehyde and their tunneling splittings with the multi-configuration time-dependent Hartree method

Schröder

Meyer

2014

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“…35,[47][48][49] For more details about the potfit algorithm, discussion of weights, error analysis, etc., the reader is referred to the articles. Here, the kinetic energy operator in polyspherical Radau coordinates has the desired product form ͑see below͒.…”

Section: B Hamiltonian and Coordinatesmentioning

confidence: 99%

Full-dimensional quantum dynamics of vibrationally highly excited NHD2

Marquardt

Sanrey

Gatti

et al. 2010

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We report on full-dimensional vibrational quantum dynamics of the highly excited ammonia isotopologue NHD(2) using a newly developed potential energy surface and the MCTDH program package. The calculations allow to realistically simulate an infrared laser induced stereomutation reaction at the pyramidal nitrogen atom in the femtosecond time domain. Our results allow for a thorough qualitative and quantitative understanding of infrared photoinduced stereomutation kinetics, the underlying quantum dynamics, and the reaction mechanisms. Comparison is made with a previous, reduced dimensionality study of the same reaction [R. Marquardt, M. Quack, I. Thanopulos, and D. Luckhaus, J. Chem. Phys. 118, 643 (2003)], and it is shown that slight variances of reduced spaces lead to significantly different kinetics. Because the quantum dynamics depends subtly on variances of reduced spaces, reduced dimensionality treatments are not reliable even for qualitative predictions of the stereomutation kinetics. The first direct comparison between the Multiconfigurational Time Dependent Hartree [M. H. Beck, A. Jäckle, G. A. Worth et al., Phys. Rep. 324, 1 (2000)] and Unimolecular Reactions Induced by Monochromatic Infrared Radiation [M. Quack and E. Sutcliffe, QCPE Bulletin 6, 98 (1986)] program packages on a specific, four dimensional quantum dynamical problem allows for their full validation in the present work.

“…[1][2][3][4] Sometimes IVR proceeds via very specific pathways. More recently, it was demonstrated that the Heidelberg package 19 of the multiconfiguration time-dependent Hartree ͑MCTDH͒ algorithm [20][21][22][23][24] is an efficient tool to investigate the IVR in systems such as a 9D model of toluene 25 or fluoroform, 26 HONO, [27][28][29] HFCO and DFCO, 30,31 and H 2 CS ͑Ref. Much theoretical effort has been directed toward modeling these systems and to further develop general methods of molecular dynamics which, coupled with quantum chemistry calculations, could predict the vibrational states leading to a desired reaction path ͑see Lehmann et al, 1 Uzer and Miller, 2 and Quack 3 for reviews which cover theoretical and experimental studies on several molecules͒.…”

Section: Computation Of Vibrational Energy Levels and Eigenstates Of mentioning

confidence: 99%

Computation of vibrational energy levels and eigenstates of fluoroform using the multiconfiguration time-dependent Hartree method

Doriol

Gatti

Iung

et al. 2008

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130

101

A theoretical study of the vibrational spectrum of the CHF(3) molecule is carried out with the aid of the multiconfiguration time-dependent Hartree (MCTDH) algorithm. In order to obtain the eigenvalues and the eigenstates, recent developments in the MCTDH improved relaxation method in a block form are exploited. Around 80 eigenvalues are reported, which are converged with a very high accuracy. The results obtained with our study are compared with those of a previous work using the wave operator sorting algorithm approach. The present investigation exemplifies the robustness and the accuracy of the improved relaxation method.