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Compare vibrational frequencies for two calculations for H2OH2O (water dimer)


A = HF/6-31G*
B = MP2/6-31G*

scale factors=0.8985, 0.943 0.260
  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 3662 77.4 1.021   1.079 1.076 0.003 1.003   113.16 88.95 1.272
2 A A'   3653 3547 105.6 1.030   1.046 1.045 0.001 1.001   30.15 15.75 1.914
3 A A'   3620 3496 123.9 1.035   1.049 1.051 -0.001 0.999   184.77 216.76 0.852
4 A A'   1665 1666 -1.6 0.999   1.078 1.078 0.000 1.000   104.02 89.15 1.167
5 A A'   1639 1634 5.3 1.003   1.082 1.082 0.000 1.000   114.67 87.56 1.310
6 A A'   345 412 -67.4 0.836   1.102 1.081 0.021 1.020   95.22 40.27 2.365
7 A A'   163 202 -38.7 0.808   3.389 3.129 1.083   121.68 171.24 0.711
8 A A'   122 136 -13.8 0.899   1.275 1.343 -0.069 0.949   262.39 262.02 1.001
9 A A"   3755 3672 83.1 1.023   1.083 1.081 0.002 1.001   89.90 67.57 1.330
10 A A"   556 637 -81.0 0.873   1.046 1.042 0.005 1.004   217.41 162.80 1.335
11 A A"   128 150 -22.1 0.853   1.068 1.072 -0.003 0.997   155.14 186.08 0.834
12 A A"   104 85 19.1 1.224   1.024 1.018 0.007 1.006   62.58 47.82 1.309
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.