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III.G.7. (XIII.B.3.) (XIII.D.5.)

Compare vibrational frequencies for two calculations for CH3CN+ (Acetonitrile cation)

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 ?a ?a   25849 43232 -17383.1 0.598   1.376 1.356 0.020 1.015   0.00 0.00 0.00  
2 ?a ?a   2940 2958 -18.2 0.994   1.106 1.145 -0.039 0.966   46.57 112.32 -65.75 0.415
3 ?a ?a   2842 2841 1.2 1.000   1.029 1.036 -0.007 0.993   106.21 305.73 -199.52 0.347
4 ?a ?a   2467 2824 -357.0 0.874   1.013 8.474 -7.461 0.120   426.06 433.14 -7.08 0.984
5 ?a ?a   1997 2407 -410.0 0.830   12.300 1.009 11.291 12.188   81.27 321.93 -240.66 0.252
6 ?a ?a   1391 1367 24.0 1.018   1.110 1.142 -0.032 0.972   22.74 37.55 -14.81 0.606
7 ?a ?a   1320 1264 56.0 1.044   1.098 1.098 -0.000 1.000   61.55 125.23 -63.68 0.491
8 ?a ?a   1197 1002 195.2 1.195   1.112 1.924 -0.812 0.578   4.15 14.09 -9.94 0.294
9 ?a ?a   1011 903 107.6 1.119   1.500 3.179 -1.680 0.472   13.28 45.72 -32.44 0.290
10 ?a ?a   797 396 400.7 2.011   5.268 3.058 2.210 1.723   9.78 0.33 9.45 29.994
11 ?a ?a   368 292 76.1 1.261   3.567 5.286 -1.719 0.675   2.15 23.72 -21.57 0.091
12 ?a ?a   368 3082i 3449.6 -0.119   4.610 1.098 3.513 4.200   43.95 516.99 -473.04 0.085
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.