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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 -0.782 -0.251
  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 3548 109.4 1.031   1.051 1.046 0.005 1.005   36.39 10.91 3.334
2 A' A'   3642 3486 155.7 1.045   1.062 1.066 -0.004 0.996   311.63 372.68 0.836
3 A' A'   2952 3020 -67.9 0.978   1.098 1.100 -0.002 0.998   69.81 44.19 1.580
4 A' A'   2852 2888 -35.9 0.988   1.037 1.035 0.002 1.002   72.22 62.11 1.163
5 A' A'   1638 1631 6.7 1.004   1.082 1.082 -0.000 1.000   109.47 92.70 1.181
6 A' A'   1497 1491 5.9 1.004   1.051 1.048 0.003 1.003   2.06 1.95 1.058
7 A' A'   1473 1453 20.1 1.014   1.162 1.161 0.001 1.001   14.16 8.53 1.661
8 A' A'   1400 1403 -3.3 0.998   1.238 1.195 0.043 1.036   64.22 50.96 1.260
9 A' A'   1086 1084 1.9 1.002   1.175 1.174 0.001 1.000   10.87 12.81 0.849
10 A' A'   1078 1047 31.5 1.030   4.900 5.683 0.862   126.48 96.10 1.316
11 A' A'   240 293 -52.5 0.821   1.414 1.350 0.064 1.047   282.69 281.77 1.003
12 A' A'   146 176 -30.3 0.828   3.634 3.885 0.935   13.96 6.65 2.100
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.