Extended ab Initio Study of the Vibrational Dynamics of H+5 and D+5 Including All Vibrational Modes

Kraemer, W.P.; Spirko, V.; Bludský, Ota

doi:10.1006/jmsp.1994.1092

Cited by 23 publications

(38 citation statements)

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“…Several * Corresponding author: octavio.roncero@csic.es global potential-energy surfaces (PESs) of increasing accuracy [35][36][37][38][39][40][41] have emerged in the last years. An energy diagram for this system is shown in Fig.…”

Section: Hmentioning

confidence: 99%

“…The use of these coordinates requires the evaluation of the hyperspherical harmonics, still in development [44,45]. Another set of symmetric coordinates was developed to study the spectroscopy of H 5 + and isotopomers [36,46,47], with respect to an equilibrium geometry. These coordinates were used recently to study the predissociation dynamics [48] using a reduced-dimensional model in an adiabatic approximation, yielding very low predissociation rates.…”

Section: Hmentioning

confidence: 99%

“…Moreover, the electric dipole moment is rather flat in these two angles, so that infrared excitation will not excite these coordinates, which behave just as spectators. For all these reasons, in the calculations presented below these two angles will be frozen to φ 1 = φ 2 = 0, whose motion corresponds to the so-called internal propellerlike rotation in previous studies [36,46,75], where the same approximation was made. To maintain the formalism it will be considered that the potential is isotropic as a function of these two angles and equal to the value of the potential for…”

Section: Hmentioning

confidence: 99%

“…For the analysis of bound states we use two sets of coordinates, those used for the calculations and introduced in [36,46,48]. These hyperspherical coordinates are appropriate for the assignment of the bound states, as are those used before in the 2D model of Ref.…”

Section: Bound States and Dissociation Energymentioning

confidence: 99%

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Simulation of the infrared predissociation spectra of H5+

et al. 2012

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A quantum study of the bound states and infrared predissociation spectra of H 5 + is done using a recently proposed global and accurate potential-energy surface [Aguado et al., J. Chem. Phys. 133, 024306 (2010)]. The bound states are calculated for seven degrees of freedom using an iterative Lanczos method, yielding a dissociation energy in very good agreement with the available experimental data. The predissociation states are described by a wave-packet treatment considering a shared-proton model, in which the three-dimensional motion of the central atom is described using non-Jacobi bond coordinates. The justification of this model is that the change in the electric dipole moment is larger as a function of the motion of the central atom, responsible for the proton transfer in the H 3 + + H 2 → H 2 + H 3 + reaction. The electric dipole moment is calculated at the level of coupled-cluster theory with single and double excitations and fitted in nine dimensions to an analytical function. With it, the infrared predissociation spectrum is simulated, yielding a reasonable agreement with recent measurements.

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Section: Hmentioning

confidence: 99%

Section: Hmentioning

confidence: 99%

Section: Hmentioning

confidence: 99%

Section: Bound States and Dissociation Energymentioning

confidence: 99%

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Simulation of the infrared predissociation spectra of H5+

et al. 2012

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“…In the last years several PES's, of increasing accuracy, have appeared in the literature. [29][30][31][32][33][34][35] The exchange reaction barrier is rather low, below the zero-point energy, so that all identical nuclei can permute, subject to the symmetry constraints imposed by nuclear spin angular momenta, 23,24,26 as experimentally confirmed by measurements in plasmas at 300-500 K. 12,13 All this makes extremely difficult to perform complete quantum calculations including the 12 degrees of freedom (9 vibrational and 3 rotational), considering the whole permutation group of symmetry. For this aim, proper coordinates should be designed, as the democratic hyperspherical coordinates developed recently by Kuppermann.…”

Section: Introductionmentioning

confidence: 99%

Dynamically biased statistical model for the ortho/para conversion in the ${\rm H}_2 + {\rm H}_3^+$H2+H3+ → ${\rm H}_3^{+} +$H3++ H2 reaction

Gómez-Carrasco

González-Sánchez

Aguado

et al. 2012

The Journal of Chemical Physics

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In this work we present a dynamically biased statistical model to describe the evolution of the title reaction from statistical to a more direct mechanism, using quasi-classical trajectories (QCT). The method is based on the one previously proposed by Park and Light [J. Chem. Phys. 126, 044305 (2007)]. A recent global potential energy surface is used here to calculate the capture probabilities, instead of the long-range ion-induced dipole interactions. The dynamical constraints are introduced by considering a scrambling matrix which depends on energy and determine the probability of the identity/hop/exchange mechanisms. These probabilities are calculated using QCT. It is found that the high zero-point energy of the fragments is transferred to the rest of the degrees of freedom, what shortens the lifetime of H + 5 complexes and, as a consequence, the exchange mechanism is produced with lower proportion. The zero-point energy (ZPE) is not properly described in quasiclassical trajectory calculations and an approximation is done in which the initial ZPE of the reactants is reduced in QCT calculations to obtain a new ZPE-biased scrambling matrix. This reduction of the ZPE is explained by the need of correcting the pure classical level number of the H + 5 complex, as done in classical simulations of unimolecular processes and to get equivalent quantum and classical rate constants using Rice-Ramsperger-Kassel-Marcus theory. This matrix allows to obtain a ratio of hop/exchange mechanisms, α(T), in rather good agreement with recent experimental results by Crabtree et al. [J. Chem. Phys. 134, 194311 (2011)] at room temperature. At lower temperatures, however, the present simulations predict too high ratios because the biased scrambling matrix is not statistical enough. This demonstrates the importance of applying quantum methods to simulate this reaction at the low temperatures of astrophysical interest.

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Quantum Monte Carlo and genetic algorithm study of the potential energy surface of the H molecule

Silva

Gargano

Silva

et al. 2008

Int J of Quantum Chemistry

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ABSTRACT:In this article we present a characterization of the vibrational spectrum of the H 5 ϩ molecule using the correlation function quantum Monte Carlo (CFQMC) method and a genetic algorithm study of the topology of the potential energy surface (PES) used. The vibrational modes associated with the H 3 ϩ -H 2 torsion and stretching possess very flat minima. As a consequence the fundamental frequencies corresponding to these modes are poorly described in the harmonic approximation. In our genetic algorithm study of the PES using Cartesian coordinates we have found some unexpected minima. A careful analysis shows that, in the curvilinear coordinates in which the potential is described, some of these minima have identical coordinates. Nevertheless, they represent nonequivalent molecular geometries. The vibrational frequencies obtained in this work are not in good agreement with available experimental data as well as other computational methods. It shows that our method of detailed analysis of PESs could reveal shortcomings introduced by the use of curvilinear coordinates.

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Extended ab Initio Study of the Vibrational Dynamics of H+5 and D+5 Including All Vibrational Modes

Cited by 23 publications

References 0 publications

Simulation of the infrared predissociation spectra of H5+

Simulation of the infrared predissociation spectra of H5+

Dynamically biased statistical model for the ortho/para conversion in the ${\rm H}_2 + {\rm H}_3^+$H2+H3+ → ${\rm H}_3^{+} +$H3++ H2 reaction

Quantum Monte Carlo and genetic algorithm study of the potential energy surface of the H molecule

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