Reading a frequency calculation output file

If  frequency calculation are present in the filename.OUT MOPAC output file (corresponding to the MOPAC FORCE keyword), MOLDRAW creates the file filename.MOL under the TMP_P directory. This file is automatically read by MOLDRAW at the end of the conversion process and two new option becomes available in the View menu.

Visualize the normal modes

Select the (View--->Normal modes) menu. A popup form containing various controls to view and render the vibrational frequencies should appear.

Each mode can be selected and the atomic displacements displayed. By clicking the animate button the mode will be animated. Speed of the motion and amplitude of the displacements are also tunable. Modes can be displayed on a symmetry base.

Speed of the animation can be incresead/decreased by the +/- buttons. The amplitude of each eigenvector can be increased/decreased by the +/- buttons.   The versus of each atomic displacement can be changed by clicking on the invert eigenvector dialog.   Modes can be selected as a function of their IR and Raman activity, or by selcting a given symmetry representation.   PovRay files can be saved as a unique pseudo PovRay movie, or as a PovRay sequence of separate files along each normal mode or each mode can be saved as a PovRay arrows very similar to the picture available in MOLDRAW.   The IR and RAMAN intensities are all set to 100 within the frequency dialog, whereas the true value is shown in the bottom line of the main window (click the picture on the left).

Generate the vibrational spectrum

Select the (View--->Vibrational spectra) menu. The vibrational spectrum (IR, Raman or both) is rendered on the screen. An ASCII XY file called filename.SPT containing the spectrum in the X(frequency in reciprocal cm) Y(normalized intensity) is also generated in the tmp_p directory. The spectrum is made by using either Gaussian or Lorentzian convolution. The maximum width at half height of each Gaussian/Lorentzian can be chosen by the user.

Vibrational spectrum dialog

IR spectrum of benzene

RAMAN spectrum of benzene

You are here: Home-Navigate-Topics-MOPAC-Frequencies

Previous Topic: Import output