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

Compare vibrational frequencies for two calculations for CH3CN (Acetonitrile)

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 A1 A1   2908 2944 -36.0 0.988   1.034 1.034 -0.000 1.000   4.88 2.24 2.64 2.179
2 A1 A1   2357 2104 253.2 1.120   12.619 12.391 0.228 1.018   13.08 0.16 12.92 82.018
3 A1 A1   1405 1388 17.2 1.012   1.228 1.234 -0.006 0.995   0.64 3.32 -2.67 0.194
4 A1 A1   875 890 -15.5 0.983   4.638 4.577 0.061 1.013   8.21 1.75 6.46 4.684
5 E E   2980 3033 -52.5 0.983   1.105 1.104 0.001 1.001   3.94 0.80 3.15 4.939
6 E E   2980 3033 -52.5 0.983   1.105 1.104 0.001 1.001   3.94 0.80 3.15 4.939
7 E E   1453 1451 2.3 1.002   1.040 1.042 -0.002 0.998   9.23 10.88 -1.65 0.848
8 E E   1453 1451 2.3 1.002   1.040 1.042 -0.002 0.998   9.23 10.88 -1.65 0.848
9 E E   1055 1032 23.6 1.023   1.438 1.394 0.044 1.032   1.54 2.51 -0.97 0.612
10 E E   1055 1032 23.6 1.023   1.438 1.394 0.044 1.032   1.54 2.51 -0.97 0.612
11 E E   382 334 47.8 1.143   3.806 4.120 -0.314 0.924   1.63 0.52 1.11 3.150
12 E E   382 334 47.8 1.143   3.806 4.120 -0.314 0.924   1.63 0.52 1.11 3.150
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.