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

Compare vibrational frequencies for two calculations for HCCCN (Cyanoacetylene)

A = HF/6-31G*

B = MP2FC/6-31G*

  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 Σ Σ   3286 4010 -723.6 0.820   1.174 7.746 -6.572 0.152   66.40 4107.33 -4040.93 0.016
2 Σ Σ   2386 3099 -713.4 0.770   10.860 1.229 9.631 8.834   52.33 35.47 16.87 1.476
3 Σ Σ   2146 2339 -193.3 0.917   6.113 6.195 -0.081 0.987   3.40 717.54 -714.14 0.005
4 Σ Σ   848 898 -49.6 0.945   8.842 8.956 -0.115 0.987   43.99 147.76 -103.77 0.298
5 Π Π   829 926 -97.2 0.895   1.367 1.279 0.088 1.069   12.83 27.87 -15.04 0.460
6 Π Π   554 609 -54.6 0.910   8.570 11.808 -3.238 0.726   10.22 0.12 10.09 83.190
7 Π Π   247 245 1.7 1.007   5.334 5.422 -0.088 0.984   0.44 0.49 -0.05 0.901
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.