Transition-State Optimizations

For a tutorial example, see Locating Transition States: Part 1.

To perform transition-state searches with Jaguar, you can use either a simple quasi-Newton method that searches for the transition state nearest to the initial geometry, or quadratic synchronous transit (QST) methods, also known as synchronous transit quasi-Newton (STQN) searches. We generally recommend using QST methods any time you can provide both reactant and product geometries and a transition state guess. For recommendations, see Transition-State Search Suggestions.

It is also recommended that you change the geometry convergence criteria to standard (the default is flexible—see SCF and Geometry Convergence for more information), particularly if you plan to perform an IRC calculation after the transition state search. You can do this by setting geoconv_mode=standard in the gen section of the input file. Using the standard criteria ensures that all criteria are met.

To set up a transition-state search, click the Tasks button and browse to Quantum Mechanics → Transition State Search1 Keyword igeopt = 2 in the gen section. in the Task Tool. You can set optimization parameters that are not unique to transition-state searches in the Optimization tab. The Transition state tab contains controls for settings that are specific to transition-state searches, including selection of the reactant and product geometries. It also contains controls for the basis set, charge, and multiplicity of the system.

For information on the transition-state search options, see Transition State Search Panel. For information on general settings that are useful for all types of geometry optimizations, see the Overview section of the Jaguar - Optimization Panel topic.