Setting up a transition state confirmation calculation

The LST and QST tools locate a maximum energy structure along the reaction path, but this maximum may not, in fact, be the transition state that you are looking for. You can use the TS confirmation tool to confirm that the transition state found does indeed connect your presumed reactant and product.

A TS confirmation calculation requires three structures to proceed - the reactants, the products, and the transition state. The trajectory used as input for this calculation should contain reactants in the first frame and products in the last frame. Transition state structure is taken as the current frame of this trajectory, unless the current frame is either the first or the last - in which case the penultimate frame is used as transition state. This is the frame where CASTEP TS Search calculations store the transition state determined in the synchronous transit search.

To perform a Transition State Confirmation

  1. First perform a TS Search using LST or QST. The trajectory computed by this method is used as input to the TS Confirmation. Make sure this trajectory document is in focus when you set up the TS Confirmation.
  2. Choose Modules | CASTEP | Calculation from the Materials Studio menu bar.
  3. Open the Setup tab.
  4. Set the Task to TS Confirmation.
  5. If desired, set additional options by selecting the More... button to open the CASTEP TS Confirmation dialog. Normally, the default options will yield adequate results.
  6. Click the Run button.

The Max. images is the upper limit for the number of frames. Structures that are too similar will be dropped during the calculation.

Users should be aware that TS Confirmation jobs can take a long time to complete. These jobs perform a series of geometry optimizations along the reaction pathway, requiring quite a lot of computer time.

At the end of the calculation, you can select any geometry on the reaction pathway using the chart/trajectory tools and perform subsequent calculations. In this way you could, for example, perform further geometry optimization on an interesting structure.

See Also:

Displaying trajectory and chart data
Reaction pathways
CASTEP TS Confirmation dialog