Go to BANDinput Select in the 'BAND Main' panel the 'Frequencies' preset
File → Save As... Save the project as H3_freq File → Run When it is done, click Yes to accept the new coordinates
After the calculation has finished
SCM → Spectra
There appear to be three peaks, whereas you would expect 3N degrees of freedom. With three atoms (N=3) we should have nine modes. We can examine this a bit closer
click on the 'NormalMode' menu.
So there are indeed nine vibrational modes. Only two are nonzero because only symmetrical modes are calculated by default. To see what a mode looks like
Select the mode at 1662 cm-1, either from the 'NormalMode' menu, or by clicking on it directly in the graph.
A new movie window pops up visualizing the vibrational mode.