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Compare vibrational frequencies for two calculations for CH3NH2+ (methyl amine cation)


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

scale factors=0.8985, 0.943 -0.407 1.878
  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'   3293 3298 -5.1 0.998   1.048 1.049 -0.000 1.000   113.44 103.18 1.099
2 A' A'   2988 3008 -20.5 0.993   1.090 1.073 0.017 1.016   5.60 11.53 0.486
3 A' A'   2883 2845 38.1 1.013   1.041 1.051 -0.010 0.990   11.34 63.88 0.178
4 A' A'   1584 1582 1.3 1.001   1.127 1.128 -0.002 0.999   51.75 40.74 1.270
5 A' A'   1446 1441 5.2 1.004   1.084 1.104 -0.020 0.982   17.66 21.16 0.834
6 A' A'   1401 1358 43.6 1.032   1.093 1.079 0.014 1.013   23.73 57.88 0.410
7 A' A'   1059 1039 20.1 1.019   1.356 1.763 0.769   6.83 6.43 1.063
8 A' A'   892 949 -57.1 0.940   4.539 2.661 1.706   0.84 20.47 0.041
9 A' A'   685 688 -3.4 0.995   1.163 1.150 0.013 1.011   165.44 188.79 0.876
10 A" A"   3400 3411 -10.2 0.997   1.108 1.108 0.000 1.000   216.85 203.15 1.067
11 A" A"   3038 3082 -43.1 0.986   1.113 1.113 0.001 1.001   3.87 12.61 0.307
12 A" A"   1431 1407 23.9 1.017   1.030 1.029 0.000 1.000   25.19 31.30 0.805
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.