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

Compare vibrational frequencies for two calculations for H2ONH3 (Water Ammonia 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'   3728 3650 78.6 1.022   1.075 1.072 0.003 1.003   82.81 60.21 22.60 1.375
2 A' A'   3564 3451 113.0 1.033   1.054 1.090 -0.036 0.967   315.89 7.02 308.88 45.030
3 A' A'   3436 3416 19.8 1.006   1.091 1.055 0.036 1.034   5.14 391.91 -386.77 0.013
4 A' A'   3318 3307 10.8 1.003   1.027 1.027 0.000 1.000   3.58 7.16 -3.58 0.500
5 A' A'   1678 1687 -8.3 0.995   1.076 1.075 0.001 1.001   94.53 75.57 18.96 1.251
6 A' A'   1659 1650 8.9 1.005   1.066 1.065 0.001 1.001   34.00 32.39 1.61 1.050
7 A' A'   1126 1129 -2.8 0.998   1.183 1.185 -0.002 0.998   204.81 167.01 37.80 1.226
8 A' A'   383 436 -53.3 0.878   1.074 1.077 -0.004 0.997   124.69 118.25 6.44 1.054
9 A' A'   166 198 -31.4 0.841   2.662 3.255 -0.593 0.818   19.31 13.99 5.32 1.380
10 A' A'   144 163 -19.2 0.883   1.306 1.202 0.103 1.086   46.77 51.17 -4.41 0.914
11 A" A"   3437 3451 -14.3 0.996   1.091 1.090 0.001 1.001   6.12 7.91 -1.80 0.773
12 A" A"   1656 1647 9.8 1.006   1.065 1.063 0.001 1.001   25.11 23.89 1.22 1.051
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.