A minimum has vanishing gradients and only positive eigen modes. A transition state (first-order saddle point) is characterized by having one negative mode. With a transition state search the optimizer will go uphill in the direction of the lowest (nonzero) eigen-mode and downhill in all other degrees of freedom. In our example it would follow mode 8. Let us give it a try from the minimum.
Choose in the 'BAND Main' panel the preset 'Transition State Search'
We have just calculated a Hessian (with the frequency run) so we'd better use it.
Use the panel bar Details → Geometry Convergence command Click on the folder button next to 'Initial Hessian From:' Select with the file dialog 'H3_freq.runkf'
File → Save As, use name H3_ts File → Run After it has finished: Update the coordinates in BANDinput SCM → Movie Graph → Energy
The third H atom ends up exactly in the middle of the (repeated) H1 and H2 atoms. Let us finally check that we are indeed in the transition state.
In the 'BAND Main' panel select the task 'Frequencies' Save the project as 'H3_ts_freq' and run it. When the calculation is ready: open ADFspectra and click on the 'NormalModes' menu
You should see:
We have found a geometry with vanishing gradients with one weak negative vibrational mode. We have succeeded in finding a transition state.
SCM → Close All