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

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

HF/3-21G

Frequency in cm-1
  Calculated   Experimental
Mode Number Symmetry Frequency diff Symmetry Frequency Comment
1 Σg 2451 161 Σg 2290  
2 Σg 2224 105 Σg 2119  
3 Σg 583 -109 Σg 692  
4 Σu 2367 126 Σu 2241  
5 Σu 1112 -42 Σu 1154  
6 Πg 892 388 Πg 504  
7 Πg 347 84 Πg 263  
8 Πu 645 173 Πu 472  
9 Πu 122 15 Πu 107  
The calculated vibrational frequencies were scaled by 0.9056

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.