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

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

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   2107 2020 86.4 1.043   12.000 12.000 0.000 1.000   0.00 0.00 0.00  
2 Σg Σg   918 895 23.2 1.026   12.000 12.000 0.000 1.000   0.00 0.00 0.00  
3 Σu Σu   1564 1493 70.9 1.047   12.000 12.000 0.000 1.000   142.35 491.73 -349.38 0.289
4 Πg Πg   367 370 -4.0 0.989   12.000 12.000 0.000 1.000   0.00 0.00 0.00  
5 Πg Πg   367 370 -4.0 0.989   12.000 12.000 0.000 1.000   0.00 0.00 0.00  
6 Πu Πu   188 169 19.2 1.114   12.000 12.000 0.000 1.000   25.62 16.58 9.04 1.545
7 Πu Πu   188 169 19.2 1.114   12.000 12.000 0.000 1.000   25.62 16.58 9.04 1.545
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.