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

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

A = HF/6-31G*

B = MP2/6-31G*

scale factors=0.8985, 0.943
  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   1169 1179 -10.2 0.991   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   130i 274 -404.3 -0.476   12.000 12.000 0.000 1.000   17.74 1.28 16.46 13.874
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.