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


A = HF/6-31G*
B = MP2/6-31G*

scale factors=0.8985, 0.943 -0.266 0.233
  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   2071 2796 -724.6 0.741   13.047 13.069 -0.023 0.998   0.00 0.00  
2 Σg Σg   704 695 9.2 1.013   14.450 14.422 0.028 1.002   0.00 0.00  
3 Σu Σu   1880 2804 -923.8 0.671   12.957 12.966 -0.009 0.999   1327.09 7600.40 0.175
4 Σu Σu   1546 1556 -10.0 0.994   12.744 12.736 0.008 1.001   229.87 104.47 2.200
5 Πg Πg   550 546 3.8 1.007   12.561 12.563 -0.002 1.000   0.00 0.00  
6 Πg Πg   475 527 -51.6 0.902   12.561 12.563 -0.002 1.000   0.00 0.00  
7 Πu Πu   525 551 -26.5 0.952   12.539 12.486 0.053 1.004   157.72 73.99 2.132
8 Πu Πu   477 445 32.1 1.072   12.492 12.758 0.979   67.58 96.66 0.699
9 Πu Πu   58 60 -1.4 0.976   13.228 13.235 -0.007 0.999   2.78 3.70 0.752
10 Πu Πu   33 114i 146.3 -0.287   13.176 12.943 1.018   0.47 1.73 0.269
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.