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Compare vibrational frequencies for two calculations for CH3O+ (Methoxy cation)


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

scale factors=0.8985, 0.943 -2.761
  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   2834 2654 179.8 1.068   1.018 1.017 0.001 1.001   63.12 322.11 0.196
2 A1 A1   1372 1247 124.7 1.100   1.120 1.097 0.023 1.021   31.65 144.73 0.219
3 A1 A1   678 1055 -377.5 0.642   10.609 13.370 0.793   5.03 273.92 0.018
4 E E   2950 2727 223.2 1.082   1.107 1.088 0.019 1.018   52.87 154.34 0.343
5 E E   2950 2727 223.2 1.082   1.107 1.088 0.019 1.018   52.87 154.34 0.343
6 E E   1346 1159 186.9 1.161   1.045 1.033 0.012 1.011   44.11 71.95 0.613
7 E E   1346 1159 186.9 1.161   1.045 1.033 0.012 1.011   44.11 71.95 0.613
8 E E   975 819 155.8 1.190   1.248 1.340 -0.092 0.931   0.50 13.54 0.037
9 E E   975 819 155.8 1.190   1.248 1.340 -0.092 0.931   0.50 13.54 0.037
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.