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

Compare vibrational frequencies for two calculations for NCO (isocyanato radical)

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   1760 2366 -606.6 0.744   12.732 12.998 -0.266 0.980   20.16 1008.35 -988.20 0.020
2 Σ Σ   1264 1237 26.3 1.021   14.860 14.515 0.346 1.024   1.28 1.19 0.09 1.075
3 Π Π   566 569 -2.5 0.996   12.710 12.715 -0.005 1.000   33.49 20.27 13.22 1.652
4 Π Π   498 538 -39.6 0.926   12.710 12.715 -0.005 1.000   54.82 63.84 -9.02 0.859
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.