The 1 3A′ HCN and 1 3A′ HCO+ Vibrational Frequencies and Spectroscopic Constants from Quartic Force Fields

Fortenberry, Ryan C.; Huang, Xinchuan; Crawford, T. Daniel; Lee, Timothy J.

doi:10.1021/jp309243s

Cited by 25 publications

(41 citation statements)

References 57 publications

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“…22,[24][25][26] The geometries of the stationary points are similar with the results of Rayez et al, 22 while the relative energies are much lower than theirs. For the equilibrium geometry of the 1 3 A state, our prediction (2.081 bohr, 2.447 bohr, 121.5 • ) shows a better agreement with the CCSD(T)/augcc-pV5Z results (2.081 bohr, 2.433 bohr, 120.6 • ) from Fortenberry at al.…”

Section: A Potential Energy Surfacessupporting

confidence: 84%

“…Fortenberry et al 26 Fortenberry et al 26 This work CR QFF-VPT a CR QFF-VCI b This work CR QFF-VPT a CR QFF-VCI b (n 1 , n 2, n 3 ) ( n 1 , n 2, n 3 ) (0, 0, 0) 0.0 (0, 0, 0) 0.0 (0, 1, 0 . Consequently, only the PESs corrected with the MRCI-Q/AV5Z results will be discussed below.…”

Section: A Potential Energy Surfacesmentioning

confidence: 99%

“…For the equilibrium geometry of the 1 3 A state, our prediction (2.081 bohr, 2.447 bohr, 121.5 • ) shows a better agreement with the CCSD(T)/augcc-pV5Z results (2.081 bohr, 2.433 bohr, 120.6 • ) from Fortenberry at al. 26 In Table II, the low-lying vibrational energy levels on our PESs are listed and compared with those obtained on the recent quartic force fields of HCN and DCN. Again, the agreement is quite good.…”

Section: A Potential Energy Surfacesmentioning

confidence: 99%

See 2 more Smart Citations

State-to-state quantum dynamics of the N(4S) + CH(X 2Π) → CN(X 2Σ+,A2Π) + H(2S) reactions

Xie

et al. 2013

The Journal of Chemical Physics

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The reactions between N((4)S) and CH(X(2)Π) lead to H((2)S) plus CN in its two lowest electronic states (X(2)Σ(+) and A(2)Π), which are responsible for the interstellar CN formation. Accurate quantum dynamics of these reactions are investigated on new global potential energy surfaces of the two lowest-lying triplet states of HCN (1(3)A' and 1(3)A") fitted to more than 37,000 points at the internally contracted multi-reference configuration interaction level with the Davidson correction. The pathways for these highly exothermic and barrierless reactions feature both the HCN and HNC wells. Long-lived resonances supported by these wells manifest in reaction probabilities as numerous oscillations, particularly for low J partial waves. The 1(3)A" state is found to be more reactive than the 1(3)A' state, due apparently to its more attractive nature in the entrance channel. The CN products in both electronic states are highly excited in both vibrational and rotational degrees of freedom. The near forward-backward symmetric differential cross sections are consistent with a complex-forming mechanism.

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Section: A Potential Energy Surfacessupporting

confidence: 84%

Section: A Potential Energy Surfacesmentioning

confidence: 99%

Section: A Potential Energy Surfacesmentioning

confidence: 99%

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State-to-state quantum dynamics of the N(4S) + CH(X 2Π) → CN(X 2Σ+,A2Π) + H(2S) reactions

Xie

et al. 2013

The Journal of Chemical Physics

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“…In addition, they calculated some parts of the conical intersection which are energetically lower that the ground state reactants, indicating that transitions between surfaces should play an important role in the N + CH reaction dynamics . In subsequent years, different theoretical methods have been used to study the characteristics of excited triplet states of HCN . Thürwächter and Halvick presented a procedure for computing a global ab initio quasi‐diabatic representation for the reaction N + CH → CN + H .…”

Section: Reaction Dynamics Of N(4s) + Ch(x2п) → H(2s) + Cn (X2σ+ A2п)mentioning

confidence: 99%

State‐to‐state reaction dynamics for the reactions of atom N with radicals

Xie

2014

Int J of Quantum Chemistry

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Much progress has been achieved in the developments of accurate and efficient algorithms for quantum dynamics calculations in the past two decades. Based on the reliable potential energy surfaces (PESs) constructed with state-of-the-art ab initio calculations, quantum reactive scattering calculations for the atom-diatom collisions can be performed accurately at the state-to-state level. In this review, we described the general strategies of constructing a PES and the Chebyshev real wave packet method briefly, and summarized our recent studies on the PESs and state-to-state reaction dynamics for the reactions of the atom N with radicals OH, CH, and C 2 . Such barrierless complex-forming reactions are very important for understanding low-temperature reaction dynamics and still difficult to treat accurately.

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“…Although significant improvements were obtained for vibrational frequencies relative to simple QFF schemes, this method requires some prior knowledge of the PES to place additional reference points,and although some methods for automatic selection of those points have been proposed, the scheme still implies a significant increment in computational cost. A very interesting way of improving QFFs was implemented by Dateo et al and later by Fortenberry et al based on the early work by Watson, Meyer et al, and Carter and Handy, in the context of internal valence coordinates. The scheme consists of substituting single bond stretching coordinates with Morse coordinates, which present the correct asymptotic behavior, obtaining excellent fits for the vibrational frequencies to within a few cm −1 of experiment.…”

Section: Introductionmentioning

confidence: 99%

A quartic force field coordinate substitution scheme using hyperbolic sine coordinates

Armiño

Bustamante

2017

Int J of Quantum Chemistry

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Quartic force fields (QFF) are currently the most cost-effective method for the approximation of potential energy surfaces for the calculation of anharmonic vibrational energies. It is known, although, that its performance can be less than satisfactory due to limitations related to slow convergence of the series. In this article, we present a coordinate substitution scheme using a combination of Morse and sinh coordinates, well adapted for its use with cartesian normal coordinates. We derive expressions for analytical integrals for use in VSCF and VCI calculations and show that the simultaneous substitution of symmetric and antisymmetric normal coordinates by Morse and sinh coordinates, respectively, significantly improves the vibrational transition frequencies for these modes in a well-balanced fashion. The accuracy of this substitution scheme is demonstrated by comparing one and two-dimensional sections of substituted and unsubstituted QFF with ab initio potential energy grids, as well as with vibrational energy calculations using as test cases two well-studied benchmark molecules: water and formaldehyde. We conclude that the coordinate substitution scheme presented constitutes a very attractive alternative to simple QFFs in the context of cartesian normal coordinates.quantum chemistry, quartic force fields, vibrational structure | I N T R O D U C T I O NThe calculation of accurate potential energy surfaces (PES) is certainly a crucial part of the computation of anharmonic vibrational energies and wavefunctions of molecular systems. Grid representations [1] of the PES are usually the most accurate option, although its high computational cost limits its application to very small systems, as the number of energy evaluations necessary for a complete grid rises exponentially with the number of normal modes. This limitation can be reduced somewhat by the use of N-mode coupling representations, [2][3][4] or more recently, adaptive sparse grid expansions. [5] Grids may be used directly, or converted into an analytical expression either by fitting [6] or interpolation [7] procedures. For example, very high accuracy have been obtained using reproducing kernel Hilbert space interpolation coupled to a grid representation for triatomic reactive systems. [8] Grid methods, even the most efficient examples of them, are still limited to small systems, so alternatives are needed for bigger molecules.Quartic force fields (QFF), this is, fourth order Taylor expansions of the potential with respect to the normal coordinates of the system, currently represent the best trade-off of accuracy and computational cost for the representation of molecular potential energy surfaces (PES) for anharmonic vibrational structure applications. The efficiency of the QFF scheme comes from the possibility of calculating the expansion coefficients by numerical differentiation of the potential, analytical gradients, or Hessians, if available. Moreover, recently Ramakrishnan and Rauhut presented an efficient scheme for computing QFFs from multimode exp...

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The 1 ³A′ HCN and 1 ³A′ HCO⁺ Vibrational Frequencies and Spectroscopic Constants from Quartic Force Fields

Cited by 25 publications

References 57 publications

State-to-state quantum dynamics of the N(4S) + CH(X 2Π) → CN(X 2Σ+,A2Π) + H(2S) reactions

State-to-state quantum dynamics of the N(4S) + CH(X 2Π) → CN(X 2Σ+,A2Π) + H(2S) reactions

State‐to‐state reaction dynamics for the reactions of atom N with radicals

A quartic force field coordinate substitution scheme using hyperbolic sine coordinates

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