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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 = 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   1228 1147 80.9 1.071   12.000 12.000 0.000 1.000   0.00 0.00 0.00  
2 Σu Σu   2077 2054 23.8 1.012   12.000 12.000 0.000 1.000   1346.30 386.87 959.43 3.480
3 Πu Πu   137 166 -28.4 0.828   12.000 12.000 0.000 1.000   2.13 20.17 -18.03 0.106
4 Πu Πu   137 166 -28.4 0.828   12.000 12.000 0.000 1.000   2.13 20.17 -18.03 0.106
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.