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

Compare vibrational frequencies for two calculations for H2OH2O (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'   3740 3663 77.2 1.021   1.079 1.076 0.003 1.003   113.16 89.46 23.70 1.265
2 A A'   3653 3547 105.8 1.030   1.046 1.045 0.001 1.001   30.15 15.69 14.46 1.921
3 A A'   3620 3497 122.9 1.035   1.049 1.050 -0.001 0.999   184.77 215.94 -31.16 0.856
4 A A'   1665 1666 -1.7 0.999   1.078 1.078 0.000 1.000   104.02 88.76 15.26 1.172
5 A A'   1639 1634 5.5 1.003   1.082 1.082 0.000 1.000   114.67 88.07 26.60 1.302
6 A A'   345 411 -65.9 0.839   1.102 1.081 0.021 1.020   95.22 41.21 54.01 2.310
7 A A'   163 201 -37.6 0.813   3.389 3.172 0.217 1.069   121.68 167.70 -46.02 0.726
8 A A'   122 135 -13.2 0.902   1.275 1.335 -0.061 0.955   262.39 263.41 -1.03 0.996
9 A A"   3755 3672 83.1 1.023   1.083 1.081 0.002 1.001   89.90 67.64 22.26 1.329
10 A A"   556 636 -80.0 0.874   1.046 1.042 0.005 1.004   217.41 163.19 54.22 1.332
11 A A"   128 152 -23.5 0.845   1.068 1.071 -0.003 0.997   155.14 182.04 -26.90 0.852
12 A A"   104 87 17.1 1.196   1.024 1.018 0.006 1.006   62.58 51.45 11.14 1.216
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.