Minimum energy method , direct

Minimum energy method (MEM), direct molecular dynamics, Gaussian wavepacket propagation, 379-381... 

The procedure and methods for the MEP determination by the NEB and parallel path optimizer methods have been explained in detail elsewhere [25, 27], Briefly, these methods are types of chain of states methods [20, 21, 25, 26, 30, 31]. In these methods the path is represented by a discrete number of images which are optimized to the MEP simultaneously. This parallel optimization is possible since any point on the MEP is a minimum in all directions except for the reaction coordinate, and thus the energy gradient for any point is parallel to the local tangent of the reaction path. 

For all cations considered, 13C NMR spectra have been measured in solution while direct structural information on the question as to whether structure Ia, lb or Ic corresponds to a minimum energy form was completely missing. Therefore, the structural problem was solved by utilizing the ab mirio/IGLO/NMR method. Since results of this work will be reviewed in another chapter of this volume (see Chapter 7), we refrain from discussing calculated NMR data for potentially homoconjugated cyclopropyl compounds at this point. 

Huge amount of studies by means of molecular orbital (MO) calculations have been reported in the literature, which calculate the structures of reactants, products, reactive intermediates, and TSs of possible reaction pathways, as well as minimum energy paths from the TSs to both the reactant and product sides on the potential energy surface (PES). The information thus obtained, together with experimental findings, has been used to deduce reaction mechanisms. The combined use of experiment and MO calculations has become a common method for physical organic chemists. However, it should be noted that the calculated structures and energies are at OK and that therefore the information obtained from MO calculations may not directly be related to experimental observation at a finite temperature. 

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