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 Keywords
- potential energy surface
- direct dynamics
- specific reaction parameter semiempirical Hamilton
- quasiclassical trajectory study
Date of Defense 2007-09-25 Availability unrestricted Abstract The reparametization of semiempirical Hamiltonians is an emerging method usedin 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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