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

Compare vibrational frequencies for two calculations for C3H3N (acrylonitrile)

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 A' A'   3098 3140 -42.6 0.986   1.119 1.119 -0.000 1.000   4.22 1.95 2.27 2.168
2 A' A'   3050 3069 -18.9 0.994   1.095 1.094 0.001 1.001   1.43 1.07 0.36 1.337
3 A' A'   3016 3045 -28.9 0.990   1.061 1.058 0.002 1.002   2.70 0.07 2.63 37.606
4 A' A'   2343 2075 268.3 1.129   12.653 12.533 0.120 1.010   26.08 1.95 24.13 13.399
5 A' A'   1663 1601 62.0 1.039   3.939 3.794 0.145 1.038   0.17 2.69 -2.52 0.063
6 A' A'   1417 1398 18.4 1.013   1.214 1.230 -0.017 0.986   7.67 4.05 3.62 1.895
7 A' A'   1292 1273 19.6 1.015   1.298 1.300 -0.002 0.998   1.66 0.20 1.46 8.493
8 A' A'   1081 1070 10.9 1.010   1.615 1.641 -0.026 0.984   4.30 3.09 1.21 1.391
9 A' A'   839 845 -6.2 0.993   2.899 2.772 0.127 1.046   3.26 0.58 2.68 5.583
10 A' A'   567 535 32.5 1.061   4.147 4.046 0.101 1.025   0.25 0.02 0.23 11.326
11 A' A'   236 217 18.5 1.085   4.017 4.230 -0.213 0.950   4.09 2.88 1.22 1.423
12 A" A"   1017 956 61.0 1.064   1.376 1.061 0.314 1.296   27.09 32.07 -4.98 0.845
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.