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Compare vibrational frequencies for two calculations for CH3OH+ (Methyl alcohol cation)


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

scale factors=0.8985, 0.943 1.066
  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 A' A'   3367 3283 83.8 1.026   1.068 1.069 -0.001 0.999   343.02 284.36 1.206
2 A' A'   3090 3122 -32.1 0.990   1.113 1.104 0.009 1.008   14.71 21.07 0.698
3 A' A'   2906 2792 113.4 1.041   1.025 1.032 -0.007 0.993   12.43 161.86 0.077
4 A' A'   1431 1436 -5.1 0.996   1.081 1.091 -0.010 0.991   6.12 7.77 0.787
5 A' A'   1382 1284 97.8 1.076   1.070 1.103 -0.034 0.969   31.52 141.93 0.222
6 A' A'   1206 1232 -26.4 0.979   1.304 1.361 -0.057 0.958   21.01 9.85 2.134
7 A' A'   937 995 -58.1 0.942   1.119 1.104 0.015 1.013   143.36 70.17 2.043
8 A' A'   670 716 -46.2 0.936   5.957 4.892 1.218   15.13 115.90 0.131
9 A" A"   3000 2849 151.6 1.053   1.107 1.086 0.021 1.019   14.24 59.94 0.238
10 A" A"   1423 1369 53.5 1.039   1.054 1.054 0.000 1.000   33.10 54.34 0.609
11 A" A"   979 890 88.5 1.099   1.166 1.125 0.042 1.037   0.26 24.23 0.011
12 A" A"   42i 332i 290.2 0.127   1.123 1.209 -0.085 0.929   138.79 45.30 3.064
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.