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

Compare vibrational frequencies for two calculations for CH3- (methyl anion)

A = HF/6-31G*

B = MP2FC/6-31G*

  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'   2951 3039 -87.9 0.971     1.008       0.00 0.00 0.00  
2 A2" A2"   1363 1378 -15.2 0.989   1.236 1.236 0.000 1.000   7.88 14.68 -6.79 0.537
3 E' E'   3119 3217 -97.6 0.970   1.125 1.119 0.006 1.005   78.66 4.21 74.45 18.680
4 E' E'   1384 1396 -12.1 0.991     1.102       0.55 2.37 -1.82 0.233
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.