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

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 23.90 1.911
2 A A   2936 3013 -76.7 0.975   1.103 1.103 -0.000 1.000   74.62 18.92 55.70 3.944
3 A A   2932 3009 -77.1 0.974   1.103 1.103 0.001 1.001   72.14 38.05 34.09 1.896
4 A A   2929 3001 -72.4 0.976   1.103 1.103 0.000 1.000   16.82 18.64 -1.82 0.902
5 A A   2906 2965 -58.5 0.980   1.075 1.080 -0.005 0.995   43.26 20.78 22.48 2.082
6 A A   2896 2956 -59.6 0.980   1.076 1.082 -0.006 0.995   35.53 23.23 12.30 1.530
7 A A   2885 2935 -50.2 0.983   1.081 1.090 -0.009 0.992   16.86 20.48 -3.63 0.823
8 A A   2878 2931 -52.8 0.982   1.043 1.036 0.007 1.007   35.41 20.56 14.85 1.722
9 A A   2825 2866 -41.7 0.985   1.060 1.052 0.008 1.008   77.89 37.27 40.62 2.090
10 A A   2819 2863 -43.9 0.985   1.058 1.052 0.006 1.006   28.91 24.02 4.90 1.204
11 A A   2803 2839 -36.3 0.987   1.073 1.070 0.003 1.003   39.46 32.70 6.76 1.207
12 A A   1487 1485 2.4 1.002   1.057 1.053 0.004 1.004   0.79 1.56 -0.76 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.