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

Compare vibrational frequencies for two calculations for C3H6S (Thietane)

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'   2986 3030 -44.3 0.985   1.111 1.110 0.001 1.001   45.52 24.62 20.90 1.849
2 A' A'   2948 3005 -56.4 0.981   1.106 1.108 -0.002 0.998   17.11 7.18 9.93 2.384
3 A' A'   2934 2961 -26.9 0.991   1.065 1.061 0.004 1.004   16.50 13.78 2.72 1.198
4 A' A'   2908 2946 -38.4 0.987   1.060 1.060 0.000 1.000   39.04 29.96 9.08 1.303
5 A' A'   1496 1484 12.6 1.009   1.126 1.120 0.006 1.005   1.84 1.64 0.20 1.120
6 A' A'   1463 1456 6.3 1.004   1.082 1.083 -0.001 0.999   1.77 3.69 -1.92 0.480
7 A' A'   1262 1241 21.1 1.017   1.364 1.378 -0.014 0.990   4.64 2.69 1.96 1.727
8 A' A'   1189 1175 13.7 1.012   1.382 1.448 -0.065 0.955   0.67 1.50 -0.84 0.443
9 A' A'   978 981 -2.8 0.997   1.325 1.360 -0.035 0.974   2.17 3.72 -1.55 0.584
10 A' A'   907 931 -23.7 0.975   2.798 2.501 0.297 1.119   0.03 0.11 -0.08 0.269
11 A' A'   826 853 -26.7 0.969   2.185 1.819 0.367 1.202   5.65 2.86 2.79 1.975
12 A' A'   700 692 7.6 1.011   1.626 2.054 -0.429 0.791   4.41 2.51 1.89 1.752
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.