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

Compare vibrational frequencies for two calculations for Cl3- (trichloride 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 Σg Σg   244 233 10.7 1.046   34.969 34.969 0.000 1.000   0.00 0.00 0.00  
2 Σu Σu   43 276 -232.7 0.156   34.969 34.969 0.000 1.000   975.99 470.37 505.62 2.075
3 Πu Πu   155 146 8.6 1.059   34.969 34.969 0.000 1.000   4.47 1.66 2.80 2.687
4 Πu Πu   155 146 8.6 1.059   34.969 34.969 0.000 1.000   4.47 1.66 2.80 2.687
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.