On the H+F2→HF+F reaction. An <i>ab initio</i> potential energy surface

O'Neil, Stephen V.; Pearson, Peter K.; Schaefer, Henry F.; Bender, Charles F.

doi:10.1063/1.1679294

Cited by 60 publications

(12 citation statements)

References 32 publications

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“…(14). Although the barrier height calculated there agrees closely with experiment, we feel that the more extensive DZ + P calculations are in general necessary to reliably predict the important features of potential energy surfaces.…”

supporting

confidence: 63%

“…Qualitatively, the DZ basis includes two functions for each orbital of the separated atoms, i.e., for fluorine Is, is', 2s, 2s', 2pz, 2px', 2pv, 2pv', 2pz, 2pz'. This is the same basis used in our earliest calculations (13,14) of the F + H2 and H + F2 surfaces. The second basis, termed double zeta plus polarization (DZ + P), is described by the notation F(9s5pld/4s2pld), H(4s-lp/2slp).…”

mentioning

confidence: 99%

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Barrier Height for the Exchange Reaction F + HF → FH + F

O'Neil¹,

Schaefer²,

Bender

1974

Proc. Natl. Acad. Sci. U.S.A.

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There exists a body of conflicting data as to the existence or nonexistence of FHF, ClHCI, BrHBr, and IHI as chemically bound molecular species. Ab initio quantum mechanical electronic structure calculations are presented which predict linear symmetric FHF to be unstable. The barrier height for the F + HF exchange reaction is suggested to be no less than 18 kcal/mol, much larger than expected either intuitively or on the basis of certain experiments on related systems. The expected reliability of the calculations is based upon comparable results for diatomic molecules and the F + H2 and H + F2 potential energy surfaces.The two classic systems for the study of reactive quantum mechanical tunneling are (1-3) H + H2 H2 + H and H + CH4 H2 + CH3The merits of these two systems with respect to tunneling are at least three: (a) both are relatively simple reactions, (b) both have relatively high barrier heights (about 10 kcal), and (c) both involve the transfer of the lightest atom, hydrogen. Thus H + H2 and H + CH4 are amenable to detailed calculation and at thermal energies, tunneling should contribute a significant fraction of the reactive cross sections.A related system which might be considered a candidate for reactive tunneling is the F + HF --FH + F reaction. Although the experimental activation energy is not known for the above reaction, in recent years it has been assumed (1) to be low, no more than 6 kcal. There are two reasons for this assumption. The first is Johnston's bond energy bond order (BEBO) method, which predicts the 6-kcal barrier. As ab initio theorists, we tend to be skeptical of empirical schemes such as BEBO. However, Truhlar (4) has recently shown that BEBO is remarkably accurate for the H + H2 and F + H2 reactions. Not only does BEBO accurately reproduce the activation energies, but it also predicts minimum energy paths within 0.03 A of those obtained from the most elaborate available ab initio calculations (5, 6). Thus the BEBO method for these two systems is far more accurate than could have been anticipated, and one should consider seriously the 6-kcal prediction for F + HF.The second indirect piece of evidence against the existence of a substantial barrier for F + HF is the report by Pimentel and coworkers (7)

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supporting

confidence: 63%

mentioning

confidence: 99%

Barrier Height for the Exchange Reaction F + HF → FH + F

O'Neil¹,

Schaefer²,

Bender

1974

Proc. Natl. Acad. Sci. U.S.A.

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“…A study of a related reaction is that of Farantos and MurreU 22 for ( 2) They derived an explicit functional form for the ground state potential energy surface of Cl0 3 , using the six interatomic distances as variables. In this way Farantos and MurreU?2 (MF) initially predicted a minimum energy pathway with a small barrier (-7 kcal) for collinear approaches along one 0-0 bond, maintaining and 0-0-0 angle of 11 7 0 • However, kinetic stUdies of Reaction (2) indicate a lower barrier, and accordingly, MF utilized a four-body term to reduce the barrier to O.…”

Section: Introductionmentioning

confidence: 99%

“…In this way Farantos and MurreU?2 (MF) initially predicted a minimum energy pathway with a small barrier (-7 kcal) for collinear approaches along one 0-0 bond, maintaining and 0-0-0 angle of 11 7 0 • However, kinetic stUdies of Reaction (2) indicate a lower barrier, and accordingly, MF utilized a four-body term to reduce the barrier to O. 3 ~cal.…”

Section: Introductionmentioning

confidence: 99%

Mechanism of the H+O3 reaction

Chen

Wetmore

Schaefer

1981

The Journal of Chemical Physics

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The H + 0 3 reaction has played an important role in the evolution of modem chemical kinetics. Here certain aspects of the H0 3 potential energy hypersurface have been investigated using nonempirical molecular electronic structure theory. For the qualitative purposes of the present study, most wave functions were of the self-consistent-field (SCF) variety, constructed from a double zeta basis set of contracted Gaussian functions. Two low energy pathways were established for the reaction. The first involves a coplanar transition state with a nearly linear H-O-O arrangement. The second possible mechanism allows the hydrogen atom to descend perpendicularly upon the ozone molecule. The two mechanisms are evaluated in light of the current experimental understanding of the H + 0 3 reaction.

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“…The most primitive method to locate TSs is the so-called grid search on a potential energy surface (PES). , In this method the PES is evaluated on a spatial grid of points that is assumed to span the saddle point of interest whose position is found by a polynomial fit. The accuracy of the method depends on the resolution of the multidimensional grid, which makes it prohibitive for moderate molecular systems.…”

Section: Brief Historical Review Of the Methods To Locate Tsmentioning

confidence: 99%

Interplay between the Gentlest Ascent Dynamics Method and Conjugate Directions to Locate Transition States

Bofill

Ribas‐Ariño

Valero

et al. 2019

J. Chem. Theory Comput.

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An algorithm to locate transition states on a potential energy surface (PES) is proposed and described. The technique is based on the GAD method where the gradient of the PES is projected into a given direction and also perpendicular to it. In the proposed method, named GAD-CD, the projection is not only applied to the gradient but also to the Hessian matrix. Then, the resulting Hessian matrix is block diagonal. The direction is updated according to the GAD method. Furthermore, to ensure stability and to avoid a high computational cost, a trust region technique is incorporated and the Hessian matrix is updated at each iteration. The performance of the algorithm in comparison with the standard ascent dynamics is discussed for a simple two dimensional model PES. Its efficiency for describing the reaction mechanisms involving small and medium size molecular systems is demonstrated for five molecular systems of interest.

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On the H+F2→HF+F reaction. An ab initio potential energy surface

Cited by 60 publications

References 32 publications

Barrier Height for the Exchange Reaction F + HF → FH + F

Barrier Height for the Exchange Reaction F + HF → FH + F

Mechanism of the H+O3 reaction

Interplay between the Gentlest Ascent Dynamics Method and Conjugate Directions to Locate Transition States

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