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

Compare vibrational frequencies for two calculations for C4H6O (Furan, 2,3-dihydro-)

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   3100 3127 -27.1 0.991   1.109 1.107 0.003 1.002   14.85 5.70 9.14 2.604
2 A A   3074 3103 -28.5 0.991   1.089 1.089 -0.000 1.000   1.69 2.10 -0.41 0.803
3 A A   2965 3019 -54.3 0.982   1.109 1.105 0.004 1.004   60.43 28.04 32.39 2.155
4 A A   2921 2980 -58.8 0.980   1.067 1.100 -0.033 0.970   74.03 19.15 54.88 3.866
5 A A   2905 2931 -26.2 0.991   1.099 1.067 0.032 1.030   19.94 40.97 -21.03 0.487
6 A A   2880 2920 -39.6 0.986   1.063 1.065 -0.002 0.998   55.78 31.01 24.77 1.799
7 A A   1671 1599 72.3 1.045   5.527 5.419 0.108 1.020   76.72 40.65 36.07 1.887
8 A A   1510 1485 24.9 1.017   1.103 1.105 -0.002 0.998   0.43 0.28 0.15 1.553
9 A A   1483 1465 17.5 1.012   1.102 1.102 0.001 1.000   0.19 0.34 -0.15 0.551
10 A A   1402 1358 43.9 1.032   1.530 1.531 -0.001 0.999   6.17 2.43 3.74 2.541
11 A A   1315 1290 24.9 1.019   1.519 1.447 0.072 1.050   5.38 4.46 0.92 1.205
12 A A   1299 1263 35.1 1.028   1.333 1.321 0.012 1.009   7.79 6.22 1.57 1.253
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.