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

Compare vibrational frequencies for two calculations for C4+ (Carbon tetramer cation)

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 Σg Σg   2136 1975 161.0 1.082   12.000 12.000 0.000 1.000   0.00 0.00 0.00  
2 Σg Σg   853 874 -20.9 0.976   12.000 12.000 0.000 1.000   0.00 0.00 0.00  
3 Σu Σu   1202 1423 -221.8 0.844   12.000 12.000 0.000 1.000   114.49 2250.05 -2135.56 0.051
4 Πg Πg   327 263 63.7 1.242   12.000 12.000 0.000 1.000   0.00 0.00 0.00  
5 Πg Πg   244 205 38.9 1.190   12.000 12.000 0.000 1.000   0.00 0.00 0.00  
6 Πu Πu   170 133 37.8 1.285   12.000 12.000 0.000 1.000   7.70 1.58 6.13 4.880
7 Πu Πu   146 127 18.3 1.144   12.000 12.000 0.000 1.000   6.33 7.40 -1.07 0.855
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.