Interpolated VTST

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. 

Energy derivatives are essential for the computation of dynamics properties. There are several dynamics-related methods available in gamess. The intrinsic reaction coordinate (IRC) or minimum energy path (MEP) follows the infinitely damped path from a first-order saddle point (transition state) to the minima connected to that transition state. In addition to providing an analysis of the process by which a chemical reaction occurs (e.g. evolution of geometric structure and wavefunction), the IRC is a common starting point for the study of dynamics. Example are variational transition state theory (VTST [55]) and the modified Shepard interpolation method developed by Collins and co-workers... 

One of the main contributions of the SACM to the theory of unimolecular dissociation was the separation of the molecular modes into conserved and disappearing (or transitional) modes and their conversion from molecule to products. The correlation between molecular and product states has already been discussed in connection with VTST and is illustrated in table 7.4 for the case of the ethane. In SACM the energy of all the normal modes are assumed to vary smoothly according to an exponential interpolation function (Quack and Troe, 1974) ... 

This fitting of a more or less global surface is not only unnecessary for applications such as VTST but very time consuming. Direct use of the ab initio data by interpolation methods promises to facilitate the application of ab initio calculations to reaction path dynamics [12, 44, 56, 57,... 

Our third generation direct dynamics scheme is called VTST with interpolated corrections (VTST-IC) or dual-level direct dynamics (DLDD) or triple-slash (///) dynamics. This approach involves three steps [49c] ... 

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