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

Compare vibrational frequencies in CCCBDB for C4H2 (Diacetylene)

B3LYP/CEP-121G*

Frequency in cm-1
  Calculated   Experimental
Mode Number Symmetry Frequency diff Symmetry Frequency Comment
1 Σg 3353 60 Σg+ 3293  
2 Σg 2177 -7 Σg+ 2184  
3 Σg 873 -1 Σg+ 874  
4 Σu 3354 25 Σu+ 3329  
5 Σu 2016 -4 Σu+ 2020  
6 Πg 1350 723 Πg 627  
7 Πg 690 208 Πg 482  
8 Πu 882 252 Πu 630  
9 Πu 325 94 Πu 231  
The calculated vibrational frequencies were scaled by 0.9694

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.