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

Compare vibrational frequencies for two calculations for C5H12S (2-Butanethiol, 3-methyl-)

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   2960 3027 -66.2 0.978   1.100 1.101 -0.002 0.998   32.94 17.38 15.56 1.895
2 A A   2958 3024 -66.6 0.978   1.100 1.102 -0.001 0.999   39.46 21.94 17.52 1.798
3 A A   2950 3018 -68.0 0.977   1.103 1.103 -0.001 0.999   50.96 19.27 31.69 2.645
4 A A   2942 3009 -67.2 0.978   1.103 1.103 0.000 1.000   47.89 24.98 22.90 1.917
5 A A   2936 3004 -67.9 0.977   1.100 1.102 -0.002 0.998   83.93 43.42 40.51 1.933
6 A A   2925 2999 -73.4 0.976   1.102 1.103 -0.001 0.999   1.33 0.19 1.14 6.949
7 A A   2907 2930 -23.1 0.992   1.086 1.080 0.007 1.006   20.48 29.72 -9.24 0.689
8 A A   2888 2928 -40.7 0.986   1.037 1.038 -0.001 0.999   22.78 14.27 8.51 1.596
9 A A   2881 2924 -43.1 0.985   1.042 1.042 0.000 1.000   38.91 14.60 24.31 2.665
10 A A   2874 2921 -46.8 0.984   1.041 1.037 0.004 1.004   17.86 10.32 7.54 1.731
11 A A   2871 2908 -37.1 0.987   1.084 1.083 0.001 1.001   5.51 3.19 2.32 1.729
12 A A   2617 2621 -3.9 0.998   1.039 1.038 0.000 1.000   27.01 18.81 8.19 1.435
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.