Intramolecular energy transfer and the driving mechanisms for large-amplitude collective motions of clusters

Tomohiro Yanao, Wang Sang Koon, Jerrold E. Marsden

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

This paper uncovers novel and specific dynamical mechanisms that initiate large-amplitude collective motions in polyatomic molecules. These mechanisms are understood in terms of intramolecular energy transfer between modes and driving forces. Structural transition dynamics of a six-atom cluster between a symmetric and an elongated isomer is highlighted as an illustrative example of what is a general message. First, we introduce a general method of hyperspherical mode analysis to analyze the energy transfer among internal modes of polyatomic molecules. In this method, the (3n-6) internal modes of an n -atom molecule are classified generally into three coarse level gyration-radius modes, three fine level twisting modes, and (3n-12) fine level shearing modes. We show that a large amount of kinetic energy flows into the gyration-radius modes when the cluster undergoes structural transitions by changing its mass distribution. Based on this fact, we construct a reactive mode as a linear combination of the three gyration-radius modes. It is shown that before the reactive mode acquires a large amount of kinetic energy, activation or inactivation of the twisting modes, depending on the geometry of the isomer, plays crucial roles for the onset of a structural transition. Specifically, in a symmetric isomer with a spherical mass distribution, activation of specific twisting modes drives the structural transition into an elongated isomer by inducing a strong internal centrifugal force, which has the effect of elongating the mass distribution of the system. On the other hand, in an elongated isomer, inactivation of specific twisting modes initiates the structural transition into a symmetric isomer with lower potential energy by suppressing the elongation effect of the internal centrifugal force and making the effects of the potential force dominant. This driving mechanism for reactions as well as the present method of hyperspherical mode analysis should be widely applicable to molecular reactions in which a system changes its overall mass distribution in a significant way.

Original languageEnglish
Article number144111
JournalJournal of Chemical Physics
Volume130
Issue number14
DOIs
Publication statusPublished - 2009
Externally publishedYes

Fingerprint

Isomers
Energy transfer
energy transfer
Kinetic energy
isomers
Molecules
twisting
mass distribution
Chemical activation
gyration
Atoms
Potential energy
Shearing
centrifugal force
polyatomic molecules
Elongation
deactivation
radii
kinetic energy
Geometry

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

Cite this

Intramolecular energy transfer and the driving mechanisms for large-amplitude collective motions of clusters. / Yanao, Tomohiro; Koon, Wang Sang; Marsden, Jerrold E.

In: Journal of Chemical Physics, Vol. 130, No. 14, 144111, 2009.

Research output: Contribution to journalArticle

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