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

Compare vibrational frequencies for two calculations for C2N2+ (Cyanogen 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   2251 2471 -220.6 0.911   12.390 12.596 -0.206 0.984   0.00 0.00 0.00  
2 Σg Σg   871 971 -99.8 0.897   13.507 13.270 0.237 1.018   0.00 0.00 0.00  
3 Σu Σu   2118 1862 256.3 1.138   12.848 12.848 0.000 1.000   1851.33 10825.77 -8974.45 0.171
4 Πg Πg   513 605 -92.2 0.848   12.177 12.175 0.001 1.000   0.00 0.00 0.00  
5 Πg Πg   446 480 -34.4 0.928   12.177 12.175 0.001 1.000   0.00 0.00 0.00  
6 Πu Πu   218 250 -31.8 0.873   12.848 12.848 0.000 1.000   15.83 14.89 0.94 1.063
7 Πu Πu   213 166 47.0 1.283   12.848 12.848 0.000 1.000   36.00 19.06 16.94 1.889
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.