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

Compare vibrational frequencies for two calculations for CH3OHH2O (methanol water dimer)

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'   3657 3549 108.7 1.031   1.051 1.046 0.005 1.005   36.39 10.92 25.47 3.333
2 A' A'   3642 3486 155.4 1.045   1.062 1.066 -0.004 0.996   311.63 372.07 -60.44 0.838
3 A' A'   2952 3021 -68.2 0.977   1.098 1.100 -0.002 0.998   69.81 44.13 25.67 1.582
4 A' A'   2852 2888 -36.2 0.987   1.037 1.035 0.002 1.002   72.22 62.04 10.17 1.164
5 A' A'   1638 1631 6.8 1.004   1.082 1.082 -0.000 1.000   109.47 92.73 16.74 1.181
6 A' A'   1497 1491 6.0 1.004   1.051 1.048 0.003 1.003   2.06 1.94 0.12 1.060
7 A' A'   1473 1452 20.3 1.014   1.162 1.161 0.001 1.001   14.16 8.51 5.65 1.664
8 A' A'   1400 1403 -3.1 0.998   1.238 1.195 0.043 1.036   64.22 50.91 13.31 1.261
9 A' A'   1086 1084 2.0 1.002   1.175 1.174 0.001 1.000   10.87 12.81 -1.93 0.849
10 A' A'   1078 1047 31.8 1.030   4.900 5.684 -0.784 0.862   126.48 96.09 30.40 1.316
11 A' A'   240 291 -51.0 0.825   1.414 1.355 0.060 1.044   282.69 280.78 1.91 1.007
12 A' A'   146 176 -30.0 0.829   3.634 3.868 -0.234 0.940   13.96 6.81 7.16 2.051
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.