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Compare vibrational frequencies for two calculations for OCS+ (Carbonyl sulfide cation)


A = HF/6-31G*
B = MP2/6-31G*

scale factors=0.8985, 0.943 0.176 -0.366
  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 Σ Σ   2122 2941 -819.0 0.721   13.409 13.233 1.013   209.49 2764.13 0.076
2 Σ Σ   588 644 -55.6 0.914   19.038 19.404 0.981   5.89 17.39 0.339
3 Π Π   420 411 9.1 1.022   13.028 13.028 -0.000 1.000   20.70 22.96 0.901
4 Π Π   383 393 -10.6 0.973   13.028 13.028 -0.000 1.000   26.38 9.39 2.809
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.