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Release 22May 2022
NIST Standard Reference Database 101
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III.G.7. (XIII.B.3.) (XIII.D.5.)

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

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 A' A'   2999 3062 -63.2 0.979   1.099 1.103 -0.003 0.997   20.58 6.65 13.93 3.094
2 A' A'   2875 2924 -49.3 0.983   1.038 1.033 0.004 1.004   51.29 37.87 13.42 1.354
3 A' A'   2224 2239 -15.2 0.993   13.403 13.611 -0.208 0.985   750.57 283.42 467.15 2.648
4 A' A'   1475 1468 6.5 1.004   1.049 1.050 -0.001 0.999   15.14 13.18 1.96 1.149
5 A' A'   1440 1413 27.0 1.019   1.168 1.153 0.014 1.012   14.23 14.23 -0.00 1.000
6 A' A'   1248 1260 -12.1 0.990   10.656 10.072 0.584 1.058   307.20 110.48 196.72 2.781
7 A' A'   1140 1109 31.5 1.028   1.444 1.365 0.079 1.058   11.06 9.77 1.29 1.133
8 A' A'   913 882 31.5 1.036   5.309 6.364 -1.055 0.834   29.17 19.10 10.07 1.527
9 A' A'   662 647 15.5 1.024   6.885 8.185 -1.301 0.841   8.26 9.37 -1.11 0.882
10 A' A'   247 219 27.8 1.127   4.278 4.264 0.014 1.003   5.07 9.51 -4.44 0.533
11 A" A"   2926 3003 -77.0 0.974   1.107 1.108 -0.001 0.999   51.96 22.07 29.89 2.354
12 A" A"   1477 1465 12.3 1.008   1.046 1.049 -0.004 0.997   5.17 6.73 -1.55 0.769
13 A" A"   1099 1081 17.7 1.016   1.253 1.247 0.007 1.006   2.00 0.19 1.81 10.446
14 A" A"   601 522 79.5 1.152   13.372 13.084 0.288 1.022   23.70 7.54 16.16 3.145
15 A" A"   103 140 -37.8 0.731   1.181 1.203 -0.022 0.981   1.39 0.92 0.47 1.509
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.