Title page for ETD etd-10092007-111213

Type of Document Master's Thesis
Author Weiss, Paula
Author's Email Address pweiss@vt.edu
URN etd-10092007-111213
Title Ab initio and Direct Quasiclassical Trajectory Study of the F + CH4 → HF + CH3 and F + C2H6 → HF + C2H5 Reactions
Degree Master of Science
Department Chemistry
Advisory Committee
Advisor Name Title
Troya, Diego Committee Chair
Crawford, Daniel T. Committee Member
Gandour, Richard D. Committee Member
Morris, John R. Committee Member
Valeyev, Eduard Faritovich Committee Member
  • potential energy surface
  • direct dynamics
  • specific reaction parameter semiempirical Hamilton
  • quasiclassical trajectory study
Date of Defense 2007-09-25
Availability unrestricted
The reparametization of semiempirical Hamiltonians is an emerging method used

in direct dynamics studies. The use of semiempirical Hamiltonians in direct dynamics

studies diminishes the computational cost of trajectory calculations and negates the need

for an analytical potential energy surface when performing reaction dynamics studies.

The reparametization of semiempirical Hamiltonians increases the agreement with

experiment and high level ab initio theory. We have chosen to create one set of new

parameters that apply to two related reactions, F + CH4 → HF + CH3 and F + C2H6 → HF

+ C2H5. We have performed an electronic structure study for these reactions. The ab

initio data obtained from the electronic structure study is then used as the reference for a

reparametization of the PM3 Hamiltonian. The reparametization has improved the ab

initio and PM3 reaction energy and potential energy surface scan agreement. This new

set of parameters for PM3 (SRP-PM3) is used to perform a direct quasiclassical trajectory

study of the reactions. The vibrational and rotational HF distributions calculated using

SRP-PM3 are compared with experiments. We have observed an improvement in the

agreement with experimental vibrational distributions but have seen no change in the

rotational distributions.

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