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Compare vibrational frequencies for two calculations for CH3N3 (methyl azide)


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

scale factors=0.8985, 0.943 -0.208 0.584 -1.055 -1.301
  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'   2999 3062 -63.2 0.979   1.099 1.103 -0.003 0.997   20.58 6.65 3.094
2 A' A'   2875 2924 -49.3 0.983   1.038 1.033 0.004 1.004   51.29 37.87 1.354
3 A' A'   2224 2239 -15.2 0.993   13.403 13.611 0.985   750.57 283.42 2.648
4 A' A'   1475 1468 6.5 1.004   1.049 1.050 -0.001 0.999   15.14 13.18 1.149
5 A' A'   1440 1413 27.0 1.019   1.168 1.153 0.014 1.012   14.23 14.23 1.000
6 A' A'   1248 1260 -12.1 0.990   10.656 10.072 1.058   307.20 110.48 2.781
7 A' A'   1140 1109 31.5 1.028   1.444 1.365 0.079 1.058   11.06 9.77 1.133
8 A' A'   913 882 31.5 1.036   5.309 6.364 0.834   29.17 19.10 1.527
9 A' A'   662 647 15.5 1.024   6.885 8.185 0.841   8.26 9.37 0.882
10 A' A'   247 219 27.8 1.127   4.278 4.264 0.014 1.003   5.07 9.51 0.533
11 A" A"   2926 3003 -77.0 0.974   1.107 1.108 -0.001 0.999   51.96 22.07 2.354
12 A" A"   1477 1465 12.3 1.008   1.046 1.049 -0.004 0.997   5.17 6.73 0.769
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.