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Compare vibrational frequencies for two calculations for Si2H2 (disilyne)


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)   Raman Activity (Å4/u)
mode number A B   A B diff. ratio   A B diff. ratio   A B diff. ratio   A B diff. ratio
1 Σg Σg   2260 2268 -8.1 0.996   1.051 1.051 0.000 1.000   0.00 0.00 0.00     237.04 286.42 -49.38 0.828
2 Σg Σg   749 689 60.0 1.087   13.009 13.041 -0.032 0.998   0.00 0.00 0.00     125.88 44.77 81.10 2.811
3 Σu Σu   2256 2266 -9.9 0.996   1.043 1.043 0.000 1.000   13.11 1.41 11.70 9.312   0.00 0.00 0.00  
4 Πg Πg   494i 560i 66.8 0.881   1.224 1.220 0.004 1.003   0.00 0.00 0.00     100.86 51.07 49.79 1.975
5 Πg Πg   494i 560i 66.8 0.881   1.224 1.220 0.004 1.003   0.00 0.00 0.00     100.86 51.07 49.79 1.975
6 Πu Πu   471 381 90.2 1.237   1.043 1.043 0.000 1.000   0.05 3.28 -3.23 0.015   0.00 0.00 0.00  
7 Πu Πu   471 381 90.2 1.237   1.043 1.043 0.000 1.000   0.05 3.28 -3.23 0.015   0.00 0.00 0.00  
scaled by     0.8985 0.943
19 08 20 15 07

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.