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Compare vibrational frequencies for two calculations for CH3CHN (methylmethaniminyl radical)


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

scale factors=0.8985, 0.943 -8.048 0.266 0.136 -0.236 0.363
  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'   2972 3059 -86.2 0.972   1.103 1.105 -0.002 0.998   17.10 4.07 4.196
2 A' A'   2912 2946 -33.9 0.989   1.082 1.035 0.047 1.045   17.14 4.43 3.871
3 A' A'   2885 2909 -24.2 0.992   1.037 1.085 -0.048 0.956   20.47 17.68 1.158
4 A' A'   1506 2000 -494.5 0.753   2.471 10.520 0.235   7.88 65.11 0.121
5 A' A'   1446 1454 -7.7 0.995   1.311 1.045 1.255   2.31 12.21 0.189
6 A' A'   1393 1368 25.1 1.018   1.256 1.242 0.013 1.011   2.53 5.84 0.433
7 A' A'   1219 1237 -18.3 0.985   1.297 1.161 1.117   3.07 3.24 0.947
8 A' A'   1050 1045 5.7 1.005   1.837 2.073 0.886   13.14 11.60 1.133
9 A' A'   876 904 -28.0 0.969   2.252 1.889 1.192   2.22 1.37 1.619
10 A' A'   426 424 1.6 1.004   3.365 3.438 -0.073 0.979   20.31 21.78 0.932
11 A" A"   2938 3029 -91.0 0.970   1.102 1.103 -0.001 0.999   22.74 5.97 3.807
12 A" A"   1458 1455 2.7 1.002   1.046 1.046 -0.001 0.999   7.65 11.03 0.694
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.