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Journal ArticleDOI

The stable states picture of chemical reactions. II. Rate constants for condensed and gas phase reaction models

Richard F. Grote, +1 more
- 15 Sep 1980 - 
- Vol. 73, Iss: 6, pp 2715-2732
TLDR
In this paper, the stable states picture (SSP) was used to derive the time correlation function (tcf) for the rate constant κ for a wide variety of gas and solution phase reaction models.
Abstract
The time correlation function (tcf) formulas for rate constants κ derived via the stable states picture (SSP) of chemical reactions are applied to a wide variety (a–d) of gas and solution phase reactionmodels. (a) For gas phase bimolecular reactions, we show that the flux tcf governing κ corresponds to standard numerical trajectory calculation methods. Alternate formulas for κ are derived which focus on saddle point surfaces, thus increasing computational efficiency. Advantages of the SSP formulas for κ are discussed. (b) For gas phase unimolecular reactions, simple results for κ are found in both the strong and weak coupling collision limits; the often ignored role of product stabilization is exposed for reversible isomerizations. The SSP results correct some standard weak coupling rate constant results by as much as 50%. (c) For barrier crossing reactions in solution, we evaluate κ for a generalized (non‐Markovian) Langevin description of the dynamics. For several realistic models of time dependent friction, κ differs dramatically from the popular Kramers constant friction predictions; this has important implications for the validity of transition state theory. (d) For solutionreactions heavily influenced by spatial diffusion, we show that the SSP isolates short range reaction dynamics of interest and includes important barrier region effects in structural isomerizations often missed in standard descriptions.

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Citations
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Journal ArticleDOI

Landscape equivalent of the shoving model.

TL;DR: It is shown that the shoving model expression for the average relaxation time of viscous liquids, according to which the activation energy is proportional to the instantaneous shear modulus, follows largely from a classical "landscape" estimation of barrier heights from curvature at energy minima.
Journal ArticleDOI

Hamiltonian theory for vibrational dephasing rates of small molecules in liquids

TL;DR: In this paper, the generalized Langevin equation (GLE) is rewritten as a Hamiltonian with a nonlinear system coupled to an infinite bath of harmonic oscillators, and a normal mode transformation followed by a perturbation technique is used to obtain the fluctuating system frequency.
Journal ArticleDOI

Molecular origins of internal friction effects on protein-folding rates

TL;DR: All-atom simulations of peptide and protein folding in explicit solvent find that an important contribution to this effect, explaining the viscosity dependence of helix formation and the folding of a helix-containing protein, is the insensitivity of torsion angle isomerization to solvent friction.
Journal ArticleDOI

Cis‐stilbene isomerization: Temperature dependence and the role of mechanical friction

TL;DR: In this paper, an upper limit for the cis-stilbene to trans-Stilbane barrier in nonpolar solvents was derived from an isoviscosity Arrhenius plot in n−alkanes and showed that macroscopic viscosity is a poor measure of the friction felt by the isomerizing species when changing solvent.
Journal ArticleDOI

Observation of the kramers turnover region in the isomerism of trans-stilbene in fluid ethane

TL;DR: In this article, trans-stilbene in ethane at 350 K gives the barrier crossing rates as a function of pressure in the range 0 to 170 atm, demonstrating a peak in the rate at 120 atm (a collision frequency of (6-7)×1012 s−1, or a viscosity of 0.03 cP).
References
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Journal ArticleDOI

Brownian motion in a field of force and the diffusion model of chemical reactions

TL;DR: In this article, a particle which is caught in a potential hole and which, through the shuttling action of Brownian motion, can escape over a potential barrier yields a suitable model for elucidating the applicability of the transition state method for calculating the rate of chemical reactions.
Book

Theory of Unimolecular Reactions

W. Forst, +1 more
BookDOI

Dynamics of Molecular Collisions

TL;DR: In this paper, the potential energy surfaces and their effect on collision processes are discussed. But the authors focus on the nonadiabatic processes in collision theory and not on the classical trajectories of trajectories.
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