Canonical variational transition-state theory . potential energy

Hu X and Hase W L 1989 Properties of canonical variational transition state theory for association reactions without potential energy barriers J. Rhys. Chem. 93 6029-38... 

While the MRCI(322)- -Q-corrected CCI4-Q PES should be accurate, direct comparison with experiment is difficult. To facilitate comparison we have employed canonical variation transition state theory [61] at the classical and adiabatic barrier using the CCI-I-Q potential for both F-I-H2 and F-I-D2. These calculations account for the zero-point energy and include a tunneling correction. The results of these calculations Me summarized in Table IX. As expected, the zero-point and tunneling corrections Me different for H2 and D2. At the classical saddle-point. 

Variational transition-state theory has been formulated on various levels [5, 23-27]. At first, there is the group of canonical VTST (CVTST) treatments, which correspond to the search for a maximum of the free energy AG(r) along the reaction path r [23, 24]. It was noticed early that for barri-erless potentials this approach leads to an overestimate of the rate constant because, in the language of SACM, channels are included that are closed. Therefore, an improved version (ICVTST) was proposed [25] that truncates Q at the position r of the minimum of (t(r) by including only states... 

Quantum dynamics effects for hydride transfer in enzyme catalysis have been analyzed by Alhambra et. al., 2000. This process is simulated using canonically variational transition-states for overbarrier dynamics and optimized multidimensional paths for tunneling. A system is divided into a primary zone (substrate-enzyme-coenzyme), which is embedded in a secondary zone (substrate-enzyme-coenzyme-solvent). The potential energy surface of the first zone is treated by quantum mechanical electronic structure methods, and protein, coenzyme, and solvent atoms by molecular mechanical force fields. The theory allows the calculation of Schaad-Swain exponents for primary (aprim) and secondary (asec) KIE... 

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