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Compare vibrational frequencies for two calculations for SiH3NH2 (Silane, amino)


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

scale factors=0.8985, 0.943 0.604
  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'   3411 3402 8.9 1.003   1.050 1.050 0.000 1.000   24.28 24.57 0.988
2 A' A'   2146 2187 -41.9 0.981   1.022 1.026 -0.004 0.996   110.37 99.65 1.108
3 A' A'   2097 2140 -43.1 0.980   1.047 1.043 0.003 1.003   309.23 234.98 1.316
4 A' A'   1585 1566 19.4 1.012   1.109 1.107 0.002 1.002   61.12 50.82 1.203
5 A' A'   983 984 -0.5 0.999   1.099 1.107 -0.008 0.993   342.14 283.48 1.207
6 A' A'   915 906 8.3 1.009   1.087 1.101 -0.014 0.987   171.12 133.90 1.278
7 A' A'   792 803 -10.9 0.986   4.459 3.855 1.157   48.48 26.78 1.810
8 A' A'   694 689 4.9 1.007   1.194 1.212 -0.018 0.985   99.35 75.23 1.321
9 A' A'   365 424 -58.7 0.862   1.201 1.208 -0.007 0.995   280.40 260.92 1.075
10 A" A"   3496 3501 -5.3 0.998   1.096 1.095 0.001 1.001   29.04 26.45 1.098
11 A" A"   2139 2195 -55.9 0.975   1.052 1.053 -0.001 0.999   270.27 202.29 1.336
12 A" A"   972 973 -1.3 0.999   1.052 1.045 0.006 1.006   127.00 88.05 1.442
13 A" A"   898 910 -12.2 0.987   1.269 1.262 0.007 1.006   86.58 70.28 1.232
14 A" A"   606 617 -10.2 0.983   1.041 1.045 -0.005 0.996   34.70 34.73 0.999
15 A" A"   156 184 -28.0 0.847   1.015 1.018 -0.003 0.997   12.59 15.31 0.822
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.