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

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

A = HF/6-31G*

B = MP2/6-31G*

scale factors=0.8985, 0.943
  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   2072 1989 83.6 1.042   13.227 13.089 0.139 1.011   1181.37 541.79 639.58 2.180
2 Σ Σ   799 847 -48.0 0.943   19.417 19.724 -0.307 0.984   46.78 7.15 39.63 6.545
3 Π Π   509 468 40.8 1.087   13.031 13.035 -0.003 1.000   19.77 3.97 15.80 4.980
4 Π Π   509 468 40.8 1.087   13.031 13.035 -0.003 1.000   19.77 3.97 15.80 4.980
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.