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

Compare vibrational frequencies for two calculations for C4H4N (pyrrolide radical)

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   3096 3126 -30.1 0.990   1.108 1.107 0.001 1.001   3.08 0.47 2.61 6.498
2 A1 A1   3065 3091 -25.4 0.992   1.095 1.097 -0.002 0.998   6.77 1.00 5.78 6.801
3 A1 A1   1548 1523 24.9 1.016   4.253 3.561 0.693 1.195   0.22 11.34 -11.12 0.019
4 A1 A1   1426 1395 31.8 1.023   3.013 4.835 -1.821 0.623   22.98 28.78 -5.80 0.798
5 A1 A1   1145 1204 -58.1 0.952   1.916 2.422 -0.506 0.791   0.29 12.45 -12.16 0.024
6 A1 A1   1067 1068 -1.0 0.999   1.380 1.765 -0.385 0.782   28.78 40.37 -11.59 0.713
7 A1 A1   985 1039 -54.0 0.948   2.331 1.349 0.982 1.728   1.40 3.61 -2.21 0.387
8 A1 A1   848 849 -0.4 1.000   5.587 4.669 0.918 1.197   13.15 12.70 0.44 1.035
9 A2 A2   940 837 103.0 1.123   1.331 1.522 -0.191 0.875   0.00 0.00 0.00  
10 A2 A2   783 778 4.8 1.006   1.540 1.181 0.359 1.303   0.00 0.00 0.00  
11 A2 A2   502 470 31.5 1.067   2.245 2.929 -0.684 0.766   0.00 0.00 0.00  
12 B1 B1   794 833 -38.9 0.953   1.589 1.767 -0.178 0.899   12.78 0.10 12.68 130.526
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.