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

Compare vibrational frequencies for two calculations for NNH (Dinitrogen monohydride)

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 Σ Σ   3272 3206 65.6 1.020   1.277 1.162 0.116 1.100   749.73 632.28 117.45 1.186
2 Σ Σ   2404 2013 391.4 1.194   4.022 5.857 -1.835 0.687   12.07 4.10 7.96 2.940
3 Π Π   723 652 71.5 1.110   1.320 1.309 0.011 1.008   169.65 157.86 11.79 1.075
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.