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

Compare vibrational frequencies for two calculations for CCH2 (vinylidene)

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   2989 3024 -34.7 0.989   1.066 1.065 0.001 1.001   21.20 46.33 -25.14 0.457
2 A1 A1   1660 1611 49.3 1.031   5.592 6.218 -0.626 0.899   63.17 79.48 -16.31 0.795
3 A1 A1   1243 1200 43.3 1.036   1.135 1.114 0.022 1.019   13.17 19.95 -6.78 0.660
4 B1 B1   833 719 114.2 1.159   1.337 1.338 -0.001 0.999   95.71 103.01 -7.30 0.929
5 B2 B2   3065 3110 -45.2 0.985   1.113 1.111 0.001 1.001   5.17 19.57 -14.39 0.264
6 B2 B2   508 334 174.0 1.521   1.329 1.331 -0.001 0.999   9.19 3.21 5.98 2.860
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.