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

Compare vibrational frequencies for two calculations for C3 (carbon trimer)

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   1228 1179 49.5 1.042   12.000 12.000 0.000 1.000   0.00 0.00 0.00  
2 Σu Σu   2243 2743 -500.7 0.817   12.000 12.000 0.000 1.000   3932.18 9050.54 -5118.36 0.434
3 Πu Πu   137 274 -136.6 0.501   12.000 12.000 0.000 1.000   2.13 1.28 0.85 1.668
4 Πu Πu   130i 274 -404.3 -0.476   12.000 12.000 0.000 1.000   17.74 1.28 16.46 13.874
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.