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Compare vibrational frequencies for two calculations for C6H4 (Benzyne)


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

scale factors=0.8985, 0.943 -1.120 -0.681 0.385 1.643 -0.287 0.244 -6.646
  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 A1 A1   3063 3070 -7.6 0.998   1.096 1.097 -0.001 0.999   5.90 4.86 1.214
2 A1 A1   3029 3049 -19.8 0.994   1.093 1.092 0.000 1.000   15.80 3.19 4.962
3 A1 A1   1987 1844 142.9 1.077   11.229 11.249 -0.021 0.998   0.04 3.26 0.013
4 A1 A1   1447 1436 11.4 1.008   2.215 3.335 0.664   0.15 0.19 0.762
5 A1 A1   1260 1324 -63.3 0.952   1.822 2.504 0.728   0.42 1.24 0.335
6 A1 A1   1118 1133 -14.9 0.987   1.474 1.089 1.353   0.64 0.78 0.823
7 A1 A1   978 1022 -43.8 0.957   4.912 3.269 1.503   30.13 20.32 1.483
8 A1 A1   967 963 3.9 1.004   2.491 2.778 0.897   4.77 2.31 2.070
9 A1 A1   603 580 22.9 1.039   7.287 7.251 0.036 1.005   0.77 0.09 8.742
10 A2 A2   988 838 150.6 1.180   1.336 1.092 1.223   0.00 0.00  
11 A2 A2   872 802 70.5 1.088   1.259 1.268 -0.010 0.992   0.00 0.00  
12 A2 A2   569 520 48.8 1.094   2.889 9.535 0.303   0.00 0.00  
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.