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

Compare vibrational frequencies for two calculations for Na2O (disodium monoxide)

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 Σg Σg   363 322 40.8 1.127   22.990 22.990 0.000 1.000   0.00 0.00 0.00  
2 Σu Σu   686 614 72.2 1.118   17.358 17.358 0.000 1.000   203.49 98.75 104.74 2.061
3 Πu Πu   44 66i 110.3 -0.672   17.358 17.358 0.000 1.000   147.51 58.68 88.84 2.514
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.