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

Compare vibrational frequencies for two calculations for CH3CONH2 (Acetamide)

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   3563 3540 23.2 1.007   1.105 1.104 0.002 1.002   51.44 40.22 11.22 1.279
2 A A   3448 3414 33.8 1.010   1.047 1.046 0.001 1.001   50.18 42.18 7.99 1.189
3 A A   2997 3062 -65.2 0.979   1.102 1.103 -0.001 0.999   10.54 3.54 7.00 2.978
4 A A   2943 3015 -72.1 0.976   1.101 1.102 -0.001 0.999   21.14 8.35 12.78 2.530
5 A A   2889 2938 -48.4 0.984   1.041 1.038 0.003 1.003   8.94 4.83 4.11 1.852
6 A A   1786 1722 64.6 1.037   9.127 8.001 1.126 1.141   439.78 251.69 188.10 1.747
7 A A   1616 1572 44.2 1.028   1.226 1.250 -0.024 0.981   120.42 99.40 21.01 1.211
8 A A   1464 1458 5.9 1.004   1.052 1.048 0.004 1.004   7.29 9.53 -2.24 0.765
9 A A   1453 1452 0.5 1.000   1.065 1.058 0.007 1.007   8.15 11.50 -3.35 0.709
10 A A   1404 1376 28.1 1.020   1.516 1.654 -0.138 0.917   72.26 83.78 -11.52 0.862
11 A A   1315 1308 7.6 1.006   2.352 2.121 0.231 1.109   149.17 91.50 57.67 1.630
12 A A   1116 1091 25.0 1.023   1.658 1.636 0.022 1.014   0.86 0.34 0.52 2.532
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.