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

Compare vibrational frequencies for two calculations for C5H10O (3-Pentanone)

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 A1 A1   2950 3027 -77.6 0.974   1.101 1.103 -0.002 0.998          
2 A1 A1   2894 2944 -50.5 0.983   1.039 1.036 0.003 1.003          
3 A1 A1   2875 2917 -41.9 0.986   1.062 1.062 -0.000 1.000          
4 A1 A1   1807 1676 130.1 1.078   11.510 9.693 1.817 1.187          
5 A1 A1   1476 1473 3.4 1.002   1.053 1.049 0.003 1.003          
6 A1 A1   1452 1443 8.8 1.006   1.095 1.100 -0.005 0.996          
7 A1 A1   1411 1390 21.0 1.015   1.267 1.261 0.006 1.005          
8 A1 A1   1354 1318 35.6 1.027   1.453 1.529 -0.075 0.951          
9 A1 A1   1091 1088 3.9 1.004   1.999 2.301 -0.302 0.869          
10 A1 A1   980 994 -13.9 0.986   2.007 1.738 0.269 1.154          
11 A1 A1   762 761 0.3 1.000   2.761 2.762 -0.001 1.000          
12 A1 A1   389 396 -6.9 0.983   3.467 3.439 0.028 1.008          
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.