CVT/SCT

KIEs calculated using TST and CVT/SCT methods were significantly different below 200 K, where virtually all the reaction was due to tunneling. 

Our studies on the three enzymes have involved the use of semi-empirical methods, using published and also SRP parameter sets. For both LADH and MADH (Figures 5-3a and b) hybrid QM/MM models were employed [8, 9, 88-90], In LADH the PES surface was calculated at the AMI level [20] but scaled by data from the HF/3-21G surface [91]. The results of the CVT calculation with the SCT correction show quite modest yet contributory degrees of tunnelling, an RTE... 

Melissas and Truhlar (1993a) studied the kinetic isotope effects (CD4/CH4) of Equation (71) using TST, CVT, and interpolated VTST (IVTST), which uses the small curvature tunneling (SCT) correction (Melissas and Truhlar 1993b). Their calculations show that accuracy of the KIE prediction increased dramatically from TST to IVTST. 

The results discussed in the previous section reveal that the reaction rate corresponding to the formation of major by-products of the oxidation reaction is important to determine the lifetime of dimethylphenol in the atmosphere. The rate constants are calculated using canonical variational transition state theory (CVT) with small curvature tunneling (SCT) corrections over the temperature range of 278-350 K. As described in Figure 19.2, the formation of product channels consists of four reaction channels. The rate constants for the formation of alkyl radical (11), peroxy radical (12), m-cresol and the product channels are designated as k, ki2, and kp, respectively, and are summarized in Tables 19.2 and 19.3. The reaction path properties and rate constant obtained for the most favorable product channels, P5 and P6, are discussed in detail. 

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