Comparisons of classical chemical dynamics simulations of the unimolecular decomposition of classical and quantum microcanonical ensembles

The Journal of Chemical Physics
Paranjothy Manikandan, William L Hase

Abstract

Previous studies have shown that classical trajectory simulations often give accurate results for short-time intramolecular and unimolecular dynamics, particularly for initial non-random energy distributions. To obtain such agreement between experiment and simulation, the appropriate distributions must be sampled to choose initial coordinates and momenta for the ensemble of trajectories. If a molecule's classical phase space is sampled randomly, its initial decomposition will give the classical anharmonic microcanonical (RRKM) unimolecular rate constant for its decomposition. For the work presented here, classical trajectory simulations of the unimolecular decomposition of quantum and classical microcanonical ensembles, at the same fixed total energy, are compared. In contrast to the classical microcanonical ensemble, the quantum microcanonical ensemble does not sample the phase space randomly. The simulations were performed for CH(4), C(2)H(5), and Cl(-)---CH(3)Br using both analytic potential energy surfaces and direct dynamics methods. Previous studies identified intrinsic RRKM dynamics for CH(4) and C(2)H(5), but intrinsic non-RRKM dynamics for Cl(-)---CH(3)Br. Rate constants calculated from trajectories obtained by the tim...Continue Reading

References

Mar 31, 2005·Annual Review of Physical Chemistry·Barry K Carpenter
Jul 20, 2006·The Journal of Chemical Physics·Andreas BachPeter Chen
Sep 30, 2008·The Journal of Physical Chemistry. a·J MikoschR Wester
Feb 27, 2009·The Journal of Physical Chemistry. a·Upakarasamy Lourderaj, William L Hase
May 2, 2009·The Journal of Chemical Physics·Gregory S EzraStephen Wiggins
Apr 19, 2011·The Journal of Physical Chemistry. a·J C Lorquet

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Citations

Sep 11, 2012·The Journal of Chemical Physics·Susana Gómez-CarrascoOctavio Roncero
Aug 20, 2014·The Journal of Chemical Physics·Vladimir V Rybkin, Ulf Ekström
May 30, 2015·The Journal of Physical Chemistry. a·Xinyou MaWilliam L Hase
Nov 17, 2019·The Journal of Chemical Physics·Bhumika JayeeWilliam L Hase
May 3, 2018·The Journal of Chemical Physics·Shreyas MalpathakWilliam L Hase
Jan 13, 2015·The Journal of Physical Chemistry. a·Jing XieWilliam L Hase

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Software Mentioned

VENUS
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