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

Compare vibrational frequencies for two calculations for CCl2- (dichloromethylene anion)

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 A1 A1   491 549 -58.6 0.893   13.536 13.700 -0.164 0.988   74.28 39.50 34.78 1.880
2 A1 A1   209 234 -25.2 0.892   33.296 32.342 0.954 1.029   8.03 4.31 3.72 1.863
3 B2 B2   298 450 -152.3 0.662   13.992 13.984 0.009 1.001   451.65 270.22 181.43 1.671
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.