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IV.C.1. (XIII.D.1.)

Compare vibrational frequencies in CCCBDB for C4N2 (2-Butynedinitrile)

MP2/CEP-31G*

Frequency in cm-1
  Calculated   Experimental
Mode Number Symmetry Frequency diff Symmetry Frequency Comment
1 Σg 2145 -145 Σg 2290  
2 Σg 1899 -220 Σg 2119  
3 Σg 559 -133 Σg 692  
4 Σu 2037 -204 Σu 2241  
5 Σu 1086 -68 Σu 1154  
6 Πg 656 152 Πg 504  
7 Πg 294 31 Πg 263  
8 Πu 465 -7 Πu 472  
9 Πu 122 15 Πu 107  
The calculated vibrational frequencies were scaled by 0.9494

See section XIII.C.3 List or set vibrational scaling factors to change the scale factors used here.
See section III.B.3.c Calculate a vibrational scaling factor for a set of molecules to determine the least squares best scaling factor.
See section III.B.3.b List of vibrational scaling factors and their uncertainties for information on where the above scaling factor is from.