Interpolation between reactants and products

An alternative strategy to the free search methods that start from the saddle point and determine the path downhill is interpolating between reactants and products. In this case, the search takes as reference points the reactants and in some cases the products. There are methods that go gradually uphill looking for the saddle point and others that progressively refine the interpolation between reactants and products.

The coordinate scan explained above would be a particular case of these methods. Examples of other more sophisticated strategies are the synchronous transit methods (LST and QST), following gradient extremals, Reduced Gradient Following and walking up valleys (see a recent review by Schlegel and the references therein [138]).