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

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

mPW1PW91/3-21G

Frequency in cm-1
  Calculated   Experimental
Mode Number Symmetry Frequency diff Symmetry Frequency Comment
1 Σg 2340 50 Σg 2290  
2 Σg 2137 18 Σg 2119  
3 Σg 600 -92 Σg 692  
4 Σu 2266 25 Σu 2241  
5 Σu 1153 -1 Σu 1154  
6 Πg 910 406 Πg 504  
7 Πg 337 74 Πg 263  
8 Πu 685 213 Πu 472  
9 Πu 116 9 Πu 107  
The calculated vibrational frequencies were scaled by 0.9546

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.