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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 0.105
  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 5.71 2.599
2 A A   3074 3103 -28.6 0.991   1.089 1.089 -0.000 1.000   1.69 2.08 0.811
3 A A   2965 3019 -54.3 0.982   1.109 1.105 0.004 1.004   60.43 28.02 2.156
4 A A   2921 2980 -58.7 0.980   1.067 1.100 -0.033 0.970   74.03 19.17 3.862
5 A A   2905 2931 -26.3 0.991   1.099 1.067 0.032 1.030   19.94 40.94 0.487
6 A A   2880 2920 -39.4 0.987   1.063 1.065 -0.002 0.998   55.78 31.01 1.799
7 A A   1671 1599 72.0 1.045   5.527 5.422 1.019   76.72 40.63 1.888
8 A A   1510 1485 24.8 1.017   1.103 1.105 -0.002 0.998   0.43 0.28 1.563
9 A A   1483 1465 17.4 1.012   1.102 1.102 0.001 1.001   0.19 0.34 0.553
10 A A   1402 1358 43.9 1.032   1.530 1.530 -0.001 1.000   6.17 2.42 2.546
11 A A   1315 1290 25.0 1.019   1.519 1.448 0.072 1.050   5.38 4.48 1.200
12 A A   1299 1263 35.1 1.028   1.333 1.321 0.013 1.010   7.79 6.20 1.257
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.