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III.G.7. (XIII.B.3.) (XIII.D.5.)

Compare vibrational frequencies for two calculations for CS2 (Carbon disulfide)

A = HF/6-31G*

B = MP2FC/6-31G*

  symmetry   frequency (cm-1)   reduced mass (amu)   IR Intensity (km mol-1)
mode number A B   A B diff. ratio   A B diff. ratio   A B diff. ratio
1 Σg Σg   651 677 -25.7 0.962   31.972 31.972 0.000 1.000   0.00 0.00 0.00  
2 Σu Σu   1423 1545 -122.6 0.921   13.314 13.314 0.000 1.000   1505.55 539.03 966.52 2.793
3 Πu Πu   400 376 24.3 1.065   13.314 13.314 0.000 1.000   0.00 2.64 -2.64 0.001
4 Πu Πu   279 376 -96.9 0.742   13.314 13.314 0.000 1.000   0.66 2.64 -1.98 0.249
scaled by     0.8985 0.943

See section III.C.1 List or set vibrational scaling factors to change the scale factors used here.
See section III.C.2 Calculate a vibrational scaling factor for a given set of molecules to determine the least squares best scaling factor.