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Compare vibrational frequencies for two calculations for COH+ (Carbon Monoxide, protonated)


A = HF/6-31G*
B = MP2/6-31G*

scale factors=0.8985, 0.943 0.195
  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 Σ Σ   3306 3204 102.7 1.032   1.103 1.107 -0.004 0.996   1221.92 1093.00 1.118
2 Σ Σ   1938 1854 84.1 1.045   7.813 7.618 1.026   192.61 90.04 2.139
3 Π Π   113 299 -186.1 0.378   1.266 1.267 -0.001 0.999   317.01 296.26 1.070
4 Π Π   113 299 -186.1 0.378   1.266 1.267 -0.001 0.999   317.01 296.26 1.070
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.