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# Compare vibrational frequencies for two calculations for CH3 (Methyl radical)

### 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'   2951 3039 -87.9 0.971     1.008     0.00 0.00
2 A2" A2"   277 376 -98.9 0.737     1.236     83.24 94.03 0.885
3 E' E'   3110 3217 -107.2 0.967     1.119     11.66 4.21 2.769
4 E' E'   3110 3217 -107.2 0.967     1.119     11.66 4.21 2.769
5 E' E'   1384 1396 -12.1 0.991     1.102     0.55 2.37 0.233
6 E' E'   1384 1396 -12.1 0.991     1.102     0.55 2.37 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.