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Compare vibrational frequencies for two calculations for N3 (azide radical)


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   1352 1356 -4.8 0.996   14.003 14.003 0.000 1.000   0.00 0.00  
2 Σu Σu   1532 5855 -4323.0 0.262   14.003 14.003 0.000 1.000   654.41 0.00  
3 Πu Πu   610 566 44.6 1.079   14.003 14.003 0.000 1.000   14.70 2.62 5.617
4 Πu Πu   476 513 -37.5 0.927   14.003 14.003 0.000 1.000   17.85 8.19 2.179
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.