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

Compare vibrational frequencies for two calculations for HCCO (ketenyl radical)

A = HF/6-31G*

B = MP2FC/6-31G*

  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'   3279 3176 102.9 1.032   1.123 1.099 0.023 1.021   106.78 41.80 64.98 2.555
2 A' A'   1880 2328 -448.2 0.807   9.103 11.728 -2.626 0.776   89.18 1048.73 -959.54 0.085
3 A' A'   1255 1235 19.6 1.016   8.097 4.726 3.371 1.713   15.88 27.30 -11.43 0.582
4 A' A'   556 651 -94.4 0.855   4.006 1.295 2.711 3.093   2.10 158.86 -156.76 0.013
5 A' A'   85 583 -497.5 0.146   1.447 9.739 -8.292 0.149   168.96 29.38 139.58 5.750
6 A" A"   481 504 -23.2 0.954   3.649 4.620 -0.971 0.790   9.33 4.89 4.44 1.909
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.