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Compare vibrational frequencies for two calculations for C(CH3)3 (Tert-butyl radical)


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

scale factors=0.8985, 0.943 0.101
  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 A1 A1   2899 2957 -57.9 0.980   1.075 1.082 -0.007 0.994   70.64 47.96 1.473
2 A1 A1   2828 2870 -42.3 0.985   1.059 1.051 0.008 1.007   81.89 37.57 2.179
3 A1 A1   1476 1468 8.0 1.005   1.052 1.053 -0.001 0.999   13.25 18.76 0.706
4 A1 A1   1417 1399 18.4 1.013   1.211 1.217 -0.005 0.996   1.37 1.72 0.797
5 A1 A1   1084 1090 -6.1 0.994   1.605 1.651 -0.045 0.972   0.52 0.00 1289.250
6 A1 A1   719 746 -27.7 0.963   3.544 3.529 0.015 1.004   0.94 0.97 0.970
7 A1 A1   259 266 -7.1 0.973   2.340 2.239 1.045   2.57 3.65 0.705
8 A2 A2   2924 3000 -75.8 0.975   1.104 1.104 -0.000 1.000   0.00 0.00  
9 A2 A2   1456 1452 4.0 1.003   1.047 1.047 0.000 1.000   0.00 0.00  
10 A2 A2   949 943 5.4 1.006   1.206 1.209 -0.003 0.998   0.00 0.00  
11 A2 A2   128 153 -25.8 0.832   1.008 1.008 0.000 1.000   0.00 0.00  
12 E E   2931 3004 -72.8 0.976   1.103 1.103 0.000 1.000   71.76 36.71 1.954
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.