title: Including Torsional Anharmonicity in Canonical and Microcanonical Reaction Path Calculations.
abstract: We reformulate multistructural variational transition state theory by removing the approximation of calculating torsional anharmonicity only at stationary points. The multistructural method with torsional anharmonicity is applied to calculate the reaction-path free energy of the hydrogen abstraction from the carbon-1 position in isobutanol by OH radical. The torsional potential anharmonicity along the reaction path is taken into account by a coupled torsional potential. The calculations show that it can be critical to include torsional anharmonicity in searching for canonical and microcanonical variational transition states. The harmonic-oscillator approximation fails to yield reasonable free energy curves along the reaction path.
authors.affiliation: Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States.
authors.forename: Jingjing
authors.initials: J
authors.lastname: Zheng
authors.affiliation: Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States.
authors.forename: Donald G
authors.initials: DG
authors.lastname: Truhlar