Display Vibrations — Run FreqChk

The Results=>Vibrations menu item is used to access various spectral results from frequency calculations. It allows calculated vibrational data to be displayed as dynamic screen motions, based on information from a frequency calculation. When you have retrieved results from a Gaussian checkpoint file or formatted checkpoint file, this menu item initially displays the Display Vibrations - Run FreqChk dialog, illustrated in the figure below. Note that if you have opened a Gaussian log file, you are taken directly to the Display Vibrations dialog.

r_vib_runfchk.tif
Running FreqChk to Perform Vibrational Analysis
In some cases, this dialog precedes the Display Vibrations dialog.

This dialog is used to run the freqchk utility included with Gaussian. This utility performs vibrational analysis for the isotopologue specified in the popup menu in the left portion of the dialog (the menu is marked with a star); here, the analysis will be performed for the second isotopologue. Once complete, the modes and spectra are available for visualization via the Display Vibrations dialog.

The Save Normal Modes and Select Normal Modes items are relevant only with Gaussian 09 and later. They correspond to the Freq=SaveNormalModes and Freq=SelectNormalModes options, respectively (and to the equivalent FreqChk options). The former saves computed normal modes back to the checkpoint file, and the latter limits the vibrational analysis to the listed modes (Modes) and modes involving the listed atoms/atom types (Atoms). Use the corresponding fields to specify the mode or atoms of interest.

The Skip diagonalization of full matrix corresponds to Freq=NoDiagFull.

Once you exit the Run FreqChk dialog, the utility will run, and the Display Vibrations window will open.