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Compare vibrational frequencies for two calculations for HCONH2CN2H4 (formamide aminomethanimine dimer)


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

scale factors=0.8985, 0.943 0.775 0.131 -0.165
  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 A A   3537 3519 18.1 1.005   1.095 1.089 0.005 1.005   107.74 99.13 1.087
2 A A   3530 3502 27.1 1.008   1.091 1.087 0.004 1.004   106.49 90.92 1.171
3 A A   3391 3348 42.8 1.013   1.077 1.077 0.000 1.000   2.19 4.62 0.474
4 A A   3359 3262 96.8 1.030   1.059 1.064 -0.005 0.995   393.21 627.05 0.627
5 A A   3265 3112 152.2 1.049   1.066 1.072 -0.005 0.995   424.33 599.59 0.708
6 A A   2945 2955 -10.9 0.996   1.091 1.091 0.001 1.001   78.82 78.91 0.999
7 A A   2889 2881 8.3 1.003   1.089 1.088 0.000 1.000   149.62 164.99 0.907
8 A A   1766 1723 42.5 1.025   5.067 4.292 1.181   745.82 490.53 1.520
9 A A   1706 1684 22.0 1.013   2.357 2.227 1.059   172.64 94.14 1.834
10 A A   1647 1608 38.7 1.024   1.359 1.427 -0.068 0.952   24.34 6.54 3.721
11 A A   1632 1597 34.4 1.022   1.384 1.422 -0.038 0.973   23.94 10.66 2.246
12 A A   1423 1381 42.0 1.030   1.805 1.970 0.916   55.51 30.57 1.816
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.