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Compare vibrational frequencies for two calculations for HCCCN+ (Cyanoacetylene cation)


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

scale factors=0.8985, 0.943 -6.612 6.262 5.520 -0.116 -9.040 -4.026 5.589 1.527
  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   3154 4010 -855.7 0.787   1.132 7.743 0.146   201.13 4145.41 0.049
2 Σ Σ   1807 3100 -1292.6 0.583   7.492 1.230 6.093   100.07 36.56 2.738
3 Σ Σ   1542 2339 -797.0 0.659   11.713 6.193 1.891   428.74 718.23 0.597
4 Σ Σ   848 897 -48.9 0.945   8.842 8.957 0.987   43.99 148.50 0.296
5 Π Π   829 925 -95.9 0.896   1.367 1.278 0.088 1.069   12.83 27.92 0.460
6 Π Π   631 719 -88.7 0.877   1.292 10.332 0.125   64.38 13.56 4.747
7 Π Π   440 609 -169.0 0.722   7.781 11.807 0.659   3.81 0.12 30.870
8 Π Π   432 436 -3.9 0.991   6.899 1.309 5.269   9.34 41.05 0.228
9 Π Π   201 244 -42.7 0.825   5.327 5.426 -0.098 0.982   0.02 0.49 0.033
10 Π Π   200 240 -39.3 0.836   6.179 4.652 1.328   0.22 0.43 0.514
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.