Editing Transition state (section)

== Determining the geometry of a transition state ==

Transition state structures can be determined by searching for first-order saddle points on the potential energy surface (PES) of the chemical species of interest.<ref>{{Cite book|title=Introduction to Computational Chemistry|publisher= John Wiley and Sons Ltd|location= England|year=1999|author= Frank Jensen}}</ref> A first-order saddle point is a [[critical point (mathematics)|critical point]] of index one, that is, a position on the PES corresponding to a minimum in all directions except one. This is further described in the article [[geometry optimization]].