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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 80.8 1.070   12.000 12.000 0.000 1.000   0.00 0.00  
2 Σu Σu   2077 2054 23.7 1.012   12.000 12.000 0.000 1.000   1346.30 386.90 3.480
3 Πu Πu   137 166 -28.3 0.829   12.000 12.000 0.000 1.000   2.13 20.17 0.106
4 Πu Πu   137 166 -28.3 0.829   12.000 12.000 0.000 1.000   2.13 20.17 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.