Checklist of Methods for Finding Transition Structures

Many techniques for finding transition structures are discussed above. The following is a listing of each of these starting with those that are easiest to use and most often successful. In other words, start with number 1 and continue down the list until you And one that works. 

If the system can only be modeled feasibly by molecular mechanics, use the potential energy curve-crossing technique or a force held with transition-structure atom types. 

If the transition state can be defined by symmetry, do a normal geometry optimization calculation with the symmetry constrained. 

If the structure of the intermediate for a very similar reaction is available, use that structure with a quasi-Newton optimization. 

Quadratic synchronous transit followed by quasi-Newton. 

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