Journal ArticleDOI
Quantum and classical studies of vibrational motion of CH5+ on a global potential energy surface obtained from a novel ab initio direct dynamics approach.
TLDR
A full dimensional, ab initio based potential energy surface for CH(5) (+) and the dipole moment surfaces are fit using novel procedures that ensure the full permutational symmetry of the system.Abstract:
We report a full dimensional, ab initio based potential energy surface for CH5+. The ab initio electronic energies and gradients are obtained in direct-dynamics calculations using second-order Moller-Plesset perturbation theory with the correlation consistent polarized valence triple zeta basis. The potential energy and the dipole moment surfaces are fit using novel procedures that ensure the full permutational symmetry of the system. The fitted potential energy surface is tested by comparing it against additional electronic energy calculations and by comparing normal mode frequencies at the three lowest-lying stationary points obtained from the fit against ab initio ones. Well-converged diffusion Monte Carlo zero-point energies, rotational constants, and projections along the CH and HH bond lengths and the tunneling coordinates are presented and compared with the corresponding harmonic oscillator and standard classical molecular dynamics ones. The delocalization of the wave function is analyzed through c...read more
Citations
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Journal ArticleDOI
Permutationally invariant potential energy surfaces in high dimensionality
TL;DR: In this paper, the authors review recent progress in developing potential energy and dipole moment surfaces for polyatomic systems with up to 10 atoms, focusing on global linear least squares fitting of tens of thousands of scattered ab initio energies using a special, compact fitting basis of permutationally invariant polynomials.
Journal ArticleDOI
Modeling the Kinetics of Bimolecular Reactions
Antonio Fernández-Ramos,James A. Miller,Stephen J. Klippenstein,Stephen J. Klippenstein,Donald G. Truhlar +4 more
TL;DR: This review is concerned with the theoretical and computational modeling of bimolecular reactions, especially with generally applicable methods for kinetics (i.e., overall rates as opposed to detailed dynamics), and includes a basic theoretical framework that can be used for gas-phase thermal reactions, gas- phase microcanonical and state-selected reactions, and condensed-phase chemical reactions.
Journal ArticleDOI
Roaming is the dominant mechanism for molecular products in acetaldehyde photodissociation.
Brianna R. Heazlewood,Meredith J. T. Jordan,Scott H. Kable,Talitha M. Selby,David L. Osborn,Benjamin C. Shepler,Bastiaan J. Braams,Joel M. Bowman +7 more
TL;DR: It is shown that roaming pathways are important in the 308-nm photodissociation of CH3CHO to CH4 + CO, where the CH4 product is found to have extreme vibrational excitation, with the vibrational distribution peaked at ≈95% of the total available energy.
Journal ArticleDOI
Understanding the infrared spectrum of bare CH5
TL;DR: Comparison of the experimental spectrum at ∼110 kelvin to finite-temperature infrared spectra supports fluxionality of bare CH5+ under experimental conditions and provides a dynamical mechanism for exchange of hydrogens between CH3 tripod positions and the three-center bonded H2 moiety, which eventually leads to full hydrogen scrambling.
Journal ArticleDOI
A nested molecule-independent neural network approach for high-quality potential fits.
TL;DR: A nested neural network technique is developed in which an approximate NN potential is first fit and then another NN is used to fit the difference of the true potential and the approximate potential to fit surfaces for H2O and H2CO.
References
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Journal ArticleDOI
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Journal ArticleDOI
A comparison of the efficiency and accuracy of the quadratic configuration interaction (QCISD), coupled cluster (CCSD), and Brueckner coupled cluster (BCCD) methods
TL;DR: In this article, the Brueckner coupled-cluster (BCCD) method with single and double excitations from a closed-shell reference function (CCSD) and the corresponding quadratic configuration interaction method (QCISD) are formulated in terms of quantities which can be computed directly from the two-electron integrals in AO basis.