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Compare vibrational frequencies for two calculations for C5H11 (2-Methylbut-2-yl radical)


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   2944 3021 -76.5 0.975   1.101 1.103 -0.002 0.999   50.14 26.24 1.911
2 A A   2936 3013 -76.7 0.975   1.103 1.103 -0.000 1.000   74.62 18.99 3.929
3 A A   2932 3009 -77.1 0.974   1.103 1.103 0.001 1.001   72.14 37.95 1.901
4 A A   2929 3001 -72.4 0.976   1.103 1.103 0.000 1.000   16.82 18.67 0.901
5 A A   2906 2965 -58.5 0.980   1.075 1.080 -0.005 0.995   43.26 20.78 2.082
6 A A   2896 2956 -59.5 0.980   1.076 1.082 -0.006 0.995   35.53 23.22 1.530
7 A A   2885 2935 -50.1 0.983   1.081 1.090 -0.009 0.992   16.86 20.48 0.823
8 A A   2878 2931 -52.8 0.982   1.043 1.036 0.007 1.007   35.41 20.58 1.721
9 A A   2825 2866 -41.6 0.985   1.060 1.052 0.008 1.008   77.89 37.29 2.089
10 A A   2819 2863 -43.9 0.985   1.058 1.052 0.006 1.006   28.91 24.02 1.204
11 A A   2803 2839 -36.2 0.987   1.073 1.070 0.003 1.003   39.46 32.71 1.206
12 A A   1487 1485 2.4 1.002   1.057 1.053 0.004 1.004   0.79 1.55 0.509
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.