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

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

B3LYP/3-21G

Frequency in cm-1
  Calculated   Experimental
Mode Number Symmetry Frequency diff Symmetry Frequency Comment
1 Σg 2332 42 Σg 2290  
2 Σg 2138 19 Σg 2119  
3 Σg 601 -91 Σg 692  
4 Σu 2262 21 Σu 2241  
5 Σu 1155 1 Σu 1154  
6 Πg 912 408 Πg 504  
7 Πg 338 75 Πg 263  
8 Πu 689 217 Πu 472  
9 Πu 117 10 Πu 107  
The calculated vibrational frequencies were scaled by 0.9649

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.