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

Compare vibrational frequencies for two calculations for NNS (Nitrogen sulfide)

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 Σ Σ   2337 1707 630.0 1.369   14.003 14.067 -0.064 0.995   297.04 467.55 -170.51 0.635
2 Σ Σ   526 797 -270.4 0.661   18.985 18.869 0.116 1.006   44.93 28.15 16.78 1.596
3 Π Π   422 431 -9.5 0.978   14.392 14.468 -0.076 0.995   1.66 0.00 1.65 338.551
4 Π Π   422 431 -9.5 0.978   14.392 14.468 -0.076 0.995   1.66 0.00 1.65 338.551
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.