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

Compare vibrational frequencies for two calculations for N2O (Nitrous oxide)

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   2366 2119 247.2 1.117   14.032 14.286 -0.254 0.982   490.12 263.36 226.77 1.861
2 Σ Σ   1252 1215 36.9 1.030   15.175 14.889 0.286 1.019   164.89 7.90 156.99 20.874
3 Π Π   619 542 76.9 1.142   14.247 14.263 -0.016 0.999   19.62 4.63 14.99 4.235
4 Π Π   619 542 76.9 1.142   14.247 14.263 -0.016 0.999   19.62 4.63 14.99 4.235
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.