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

Compare vibrational frequencies for two calculations for CH3COCH3 (Acetone)

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 A1 A1   2986 3051 -64.9 0.979   1.103 1.104 -0.001 0.999   14.08 5.03 9.06 2.802
2 A1 A1   2886 2932 -46.3 0.984   1.039 1.037 0.003 1.003   11.97 4.65 7.32 2.575
3 A1 A1   1817 1689 127.1 1.075   10.563 8.720 1.843 1.211   229.46 89.53 139.93 2.563
4 A1 A1   1450 1447 3.4 1.002   1.055 1.072 -0.017 0.984   20.94 25.03 -4.09 0.837
5 A1 A1   1389 1361 28.5 1.021   1.241 1.239 0.002 1.002   8.07 14.03 -5.96 0.575
6 A1 A1   1070 1051 18.4 1.018   1.530 1.552 -0.022 0.986   0.59 0.12 0.48 5.125
7 A1 A1   760 768 -8.0 0.990   3.567 3.625 -0.059 0.984   0.04 0.79 -0.75 0.048
8 A1 A1   360 363 -2.7 0.993   2.224 2.193 0.030 1.014   1.31 1.00 0.31 1.306
9 A2 A2   2928 3003 -75.1 0.975   1.100 1.101 -0.000 1.000   0.00 0.00 0.00  
10 A2 A2   1447 1441 5.7 1.004   1.052 1.055 -0.003 0.997   0.00 0.00 0.00  
11 A2 A2   881 870 11.0 1.013   1.206 1.203 0.004 1.003   0.00 0.00 0.00  
12 A2 A2   46 56 -10.6 0.812   1.018 1.019 -0.001 0.999   0.00 0.00 0.00  
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.