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

Compare vibrational frequencies for two calculations for C3O2 (Carbon suboxide)

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   2223 2121 102.6 1.048   12.872 12.764 0.108 1.008   0.00 0.00 0.00  
2 Σg Σg   759 735 24.1 1.033   14.671 14.813 -0.143 0.990   0.00 0.00 0.00  
3 Σu Σu   2213 2344 -130.7 0.944   12.324 12.220 0.104 1.009   5424.16 2409.32 3014.84 2.251
4 Σu Σu   1625 1522 102.5 1.067   13.422 13.548 -0.126 0.991   59.46 82.05 -22.59 0.725
5 Πg Πg   604 538 65.4 1.121   12.539 12.527 0.012 1.001   0.00 0.00 0.00  
6 Πg Πg   604 538 65.4 1.121   12.539 12.527 0.012 1.001   0.00 0.00 0.00  
7 Πu Πu   612 526 86.6 1.165   12.450 12.437 0.014 1.001   163.48 55.98 107.50 2.920
8 Πu Πu   612 526 86.6 1.165   12.450 12.437 0.014 1.001   163.48 55.98 107.50 2.920
9 Πu Πu   78 100 -22.6 0.775   13.276 13.291 -0.015 0.999   0.57 0.01 0.56 40.197
10 Πu Πu   78 100 -22.6 0.775   13.276 13.291 -0.015 0.999   0.57 0.01 0.56 40.197
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.