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Compare vibrational frequencies for two calculations for C4H4N (pyrrolide radical)


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

scale factors=0.8985, 0.943 0.689 -1.829 -0.499 -0.379 0.977 0.916 -0.191 0.358 -0.678 -0.181
  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   3096 3126 -29.8 0.990   1.108 1.107 0.001 1.001   3.08 0.46 6.723
2 A1 A1   3065 3092 -26.7 0.991   1.095 1.097 -0.002 0.998   6.77 1.01 6.717
3 A1 A1   1548 1523 24.9 1.016   4.253 3.565 1.193   0.22 11.42 0.019
4 A1 A1   1426 1394 32.0 1.023   3.013 4.843 0.622   22.98 28.80 0.798
5 A1 A1   1145 1204 -58.2 0.952   1.916 2.415 0.793   0.29 12.40 0.024
6 A1 A1   1067 1067 -0.8 0.999   1.380 1.759 0.785   28.78 40.46 0.711
7 A1 A1   985 1039 -53.8 0.948   2.331 1.354 1.722   1.40 3.41 0.410
8 A1 A1   848 848 -0.3 1.000   5.587 4.671 1.196   13.15 12.72 1.033
9 A2 A2   940 836 103.7 1.124   1.331 1.522 0.874   0.00 0.00  
10 A2 A2   783 778 4.6 1.006   1.540 1.182 1.303   0.00 0.00  
11 A2 A2   502 470 31.6 1.067   2.245 2.923 0.768   0.00 0.00  
12 B1 B1   794 833 -38.3 0.954   1.589 1.770 0.898   12.78 0.09 141.669
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.