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Compare vibrational frequencies for two calculations for N3+ (azide 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   1127 1370 -243.0 0.823   14.003 14.003 0.000 1.000   0.00 0.00  
2 Σu Σu   866 816i 1682.1 -1.060   14.003 14.003 0.000 1.000   7.83 23.78 0.329
3 Πu Πu   334 455 -121.0 0.734   14.003 14.003 0.000 1.000   3.82 1.65 2.315
4 Πu Πu   334 455 -121.0 0.734   14.003 14.003 0.000 1.000   3.82 1.65 2.315
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.