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

Compare vibrational frequencies for two calculations for H2OHCOOH (Water formic acid dimer 1)

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   3757 3674 83.1 1.023   1.083 1.081 0.002 1.002   93.76 79.24 14.52 1.183
2 A A   3654 3547 106.7 1.030   1.046 1.046 0.000 1.000   26.42 21.89 4.53 1.207
3 A A   3629 3474 155.2 1.045   1.065 1.064 0.001 1.001   113.57 74.54 39.03 1.524
4 A A   3019 3022 -2.6 0.999   1.099 1.097 0.002 1.002   17.98 8.97 9.00 2.003
5 A A   1827 1731 95.2 1.055   7.765 7.550 0.215 1.028   449.62 257.78 191.84 1.744
6 A A   1644 1645 -0.5 1.000   1.081 1.081 -0.000 1.000   111.94 83.59 28.35 1.339
7 A A   1393 1356 37.4 1.028   1.151 1.131 0.020 1.017   16.87 8.92 7.95 1.892
8 A A   1280 1237 43.2 1.035   1.650 1.646 0.004 1.003   11.71 4.26 7.45 2.751
9 A A   1134 1072 62.2 1.058   3.585 3.777 -0.192 0.949   320.40 289.13 31.27 1.108
10 A A   1081 1023 58.2 1.057   1.584 1.501 0.083 1.055   1.20 3.51 -2.31 0.341
11 A A   638 657 -19.1 0.971   1.238 1.274 -0.037 0.971   211.53 173.33 38.20 1.220
12 A A   622 590 32.3 1.055   3.443 3.467 -0.024 0.993   63.52 49.66 13.86 1.279
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.