Step 4: Search for the transition state

Now you have a result file, HCN_Freq1.t21, with an initial geometry for a transition state search. This file also contains a Hessian matrix (produced with the frequencies calculation) that can be used to kick-start the TS procedure.

Bring ADFinput with the HCN_Freq1 calculation to the foreground
Select the 'Transition State Search' preset
Select the 'Files (Restart)' panel
Click the 'Select...' button
Click 'Open' (the HCN_Freq1.t21 file should already be selected)
Save the set up as HCN_TS (Save As)
Run the calculation

After the calculation has finished (again very fast), you will be asked to read the new geometry from the results file HCN_TS.t21:

Answer "Yes" to import the latest geometry
Make a note of the bond energy for the transition state (visible in the logfile)

ADFinput will now display the transition state geometry.

If you compare the bond energy with the bond energy of the optimized HCN molecule from the first calculation, the difference should be about 1.9 eV. Also check that the geometry makes sense: the C-H and C-N distances should be around 1.20 and 1.18 Angstrom and the H-C-N angle should be about 70 degrees.