return to home page

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

Compare vibrational frequencies for two calculations for C3O2 (Carbon suboxide)

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 Σg Σg   2223 2796 -572.5 0.795   12.872 13.069 -0.198 0.985   0.00 0.00 0.00  
2 Σg Σg   759 735 24.1 1.033   14.671 14.813 -0.143 0.990   0.00 0.00 0.00  
3 Σu Σu   2213 2804 -591.0 0.789   12.324 12.966 -0.642 0.951   5424.16 7600.29 -2176.13 0.714
4 Σu Σu   1625 1556 68.8 1.044   13.422 12.736 0.686 1.054   59.46 104.45 -44.99 0.569
5 Πg Πg   604 546 57.9 1.106   12.539 12.563 -0.024 0.998   0.00 0.00 0.00  
6 Πu Πu   612 551 61.1 1.111   12.450 12.486 -0.036 0.997   163.48 73.98 89.49 2.210
7 Πu Πu   525 551 -26.5 0.952   12.539 12.486 0.053 1.004   157.72 73.98 83.74 2.132
8 Πu Πu   477 526 -49.1 0.907   12.492 12.437 0.056 1.004   67.58 55.98 11.60 1.207
9 Πu Πu   58 100 -42.1 0.581   13.228 13.291 -0.063 0.995   2.78 0.01 2.77 195.817
10 Πu Πu   33 100 -67.6 0.326   13.176 13.291 -0.115 0.991   0.47 0.01 0.45 32.838
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.