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Compare vibrational frequencies for two calculations for NO2 (Nitrogen dioxide)


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   1449 1302 147.0 1.113   15.351 15.293 0.058 1.004   4.19 0.23 18.635
2 A1 A1   748 709 38.8 1.055   15.132 15.189 -0.057 0.996   14.76 7.10 2.079
3 B2 B2   1689 2141 -452.2 0.789   14.617 14.624 -0.007 0.999   757.00 1964.08 0.385
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.