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

Compare vibrational frequencies for two calculations for C4H9N (Cyclobutylamine)

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'   3339 3295 43.7 1.013   1.051 1.050 0.001 1.001   0.62 0.52 0.10 1.202
2 A' A'   2966 3033 -67.5 0.978   1.107 1.107 -0.000 1.000   79.27 29.85 49.41 2.655
3 A' A'   2936 2999 -63.0 0.979   1.109 1.109 -0.000 1.000   26.03 25.36 0.67 1.027
4 A' A'   2917 2963 -46.5 0.984   1.064 1.063 0.002 1.002   43.82 32.39 11.43 1.353
5 A' A'   2899 2943 -43.5 0.985   1.062 1.060 0.002 1.002   43.97 13.21 30.76 3.328
6 A' A'   2840 2871 -31.4 0.989   1.086 1.086 -0.000 1.000   100.61 83.85 16.76 1.200
7 A' A'   1647 1617 29.4 1.018   1.097 1.091 0.005 1.005   31.22 25.99 5.23 1.201
8 A' A'   1490 1477 13.2 1.009   1.147 1.141 0.006 1.005   2.83 4.06 -1.23 0.697
9 A' A'   1459 1451 7.3 1.005   1.092 1.086 0.007 1.006   1.63 2.65 -1.02 0.616
10 A' A'   1377 1351 25.7 1.019   1.477 1.494 -0.017 0.989   30.27 21.80 8.47 1.388
11 A' A'   1295 1257 38.3 1.031   1.558 1.626 -0.068 0.958   1.52 6.43 -4.91 0.237
12 A' A'   1220 1204 16.3 1.014   1.282 1.298 -0.016 0.988   2.98 1.09 1.89 2.732
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.