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Compare vibrational frequencies for two calculations for C4H9NO (Butanamide)


A = HF/6-31G*
B = MP2/6-31G*

scale factors=0.8985, 0.943 1.167
  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   3561 3538 22.9 1.006   1.105 1.104 0.002 1.001   49.25 39.70 1.241
2 A A   3446 3411 35.3 1.010   1.047 1.046 0.001 1.001   52.62 46.53 1.131
3 A A   2949 3012 -63.1 0.979   1.104 1.103 0.001 1.001   68.15 39.95 1.706
4 A A   2935 3010 -75.5 0.975   1.100 1.103 -0.003 0.997   58.83 31.25 1.882
5 A A   2915 2993 -77.5 0.974   1.101 1.103 -0.002 0.998   21.61 0.76 28.502
6 A A   2904 2956 -51.3 0.983   1.069 1.099 -0.030 0.973   14.09 11.74 1.200
7 A A   2896 2947 -51.5 0.983   1.098 1.066 0.033 1.031   18.41 15.80 1.165
8 A A   2872 2923 -50.9 0.983   1.042 1.036 0.005 1.005   41.66 22.08 1.887
9 A A   2865 2907 -41.6 0.986   1.059 1.061 -0.002 0.998   15.29 11.20 1.366
10 A A   1778 1711 66.9 1.039   9.641 8.474 1.138   379.35 229.97 1.650
11 A A   1615 1568 46.7 1.030   1.224 1.250 -0.027 0.978   130.37 107.84 1.209
12 A A   1485 1481 3.6 1.002   1.089 1.077 0.012 1.011   3.86 5.65 0.683
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.