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Compare vibrational frequencies for two calculations for C3H5Cl3 (Propane, 1,2,3-trichloro-)


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

scale factors=0.8985, 0.943 0.346
  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'   3033 3049 -15.7 0.995   1.110 1.110 0.000 1.000   4.34 2.49 1.742
2 A' A'   3001 3003 -2.7 0.999   1.088 1.086 0.002 1.002   3.51 2.62 1.339
3 A' A'   2968 2978 -9.6 0.997   1.061 1.061 0.000 1.000   19.15 12.02 1.593
4 A' A'   1476 1461 15.0 1.010   1.097 1.089 0.008 1.007   4.55 4.95 0.918
5 A' A'   1349 1335 14.0 1.010   1.242 1.256 -0.014 0.989   26.87 19.70 1.363
6 A' A'   1262 1253 9.4 1.007   1.146 1.151 -0.005 0.995   1.27 0.85 1.502
7 A' A'   1216 1206 10.0 1.008   1.123 1.134 -0.011 0.990   39.21 24.46 1.603
8 A' A'   1033 1038 -5.1 0.995   1.868 1.933 -0.065 0.966   2.18 2.08 1.049
9 A' A'   843 857 -14.4 0.983   2.729 2.655 0.074 1.028   14.58 11.72 1.244
10 A' A'   796 816 -20.4 0.975   4.699 4.664 0.035 1.008   2.01 1.12 1.797
11 A' A'   693 728 -34.9 0.952   7.948 7.602 1.046   161.57 88.11 1.834
12 A' A'   379 382 -3.8 0.990   2.088 2.028 0.060 1.029   0.54 0.15 3.567
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.