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

Compare vibrational frequencies for two calculations for CO2 (Carbon dioxide)

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   1364 1257 107.2 1.085   15.995 15.995 0.000 1.000   0.00 0.00 0.00  
2 Σu Σu   2323 2308 14.5 1.006   12.877 12.877 0.000 1.000   988.58 452.90 535.68 2.183
3 Πu Πu   670 600 70.3 1.117   12.877 12.877 0.000 1.000   68.93 25.53 43.40 2.700
4 Πu Πu   670 600 70.3 1.117   12.877 12.877 0.000 1.000   68.93 25.53 43.40 2.700
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.