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

Compare vibrational frequencies for two calculations for HNO2 (Nitrous acid)

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'   3667 3489 178.3 1.051   1.067 1.066 0.001 1.001   124.75 78.91 45.84 1.581
2 A' A'   1837 1567 269.6 1.172   10.382 8.401 1.981 1.236   152.17 63.98 88.20 2.379
3 A' A'   1361 1244 116.6 1.094   1.286 1.307 -0.020 0.984   262.73 198.58 64.15 1.323
4 A' A'   986 816 170.0 1.208   7.404 6.598 0.806 1.122   226.31 185.00 41.31 1.223
5 A' A'   710 594 116.5 1.196   7.797 9.695 -1.899 0.804   19.60 99.54 -79.94 0.197
6 A" A"   539 570 -31.7 0.944   1.159 1.159 -0.000 1.000   137.23 120.05 17.17 1.143
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.