Quadratic synchronous transit

HyperChein has two synch ron ons transit meth ods im piemen ted. The linear synchronous transit method (LST) searches for a maximum along a linear path between reactants and products. It may happen that this method will end up with a structure having two or more negative eigenvalues. The quadratic synchronous transit method (QSTlisan improvement of LST approach and searches for a maximum along a parabola connecting reactants and products, and for a minimum in all directions perpendicular to the parabola. 

Quadratic synchronous transit followed by quasi-Newton. 

It uses a linear or quadratic synchronous transit approach to get closer to the quadratic region of the transition state and then uses a quasi-Newton or eigenvalue-following algorithm to complete the optimization. 

Figure 14.5 Illustration of the linear and quadratic synchronous transit methods. Energy maxima and minima are denoted by and , respectively...

Illustrating the Concepts 264 11.1 Geometry Convergence 264 11.1.1 Ah Initio Methods 264 11.1.2 DFT Methods 267 14.4 Choice of Coordinates 322 14.5 Transition Structure Optimization 327 14.5.1 Methods Based on Interpolation Between Reactant and Product 327 14.5.2 Linear and Quadratic Synchronous Transit 328... 

QCISD(T) 207, 208 QCPE (Quantum Chemistry Program Exchange) 173 QM/MM model 262 QSAR (Quantitative Structure and Activity Relations) 56 QST (Quadratic Synchronous Transit)... 

Fig. 10.5. Model potential energy surface illustrating linear synchronous transit (LST) and quadratic synchronous transit (QST) paths (from Ref. [72] with permission).

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