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

Compare vibrational frequencies in CCCBDB for C4H2 (Diacetylene)

PBEPBEultrafine/6-31G*

Frequency in cm-1
  Calculated   Experimental
Mode Number Symmetry Frequency diff Symmetry Frequency Comment
1 Σg 3367 74 Σg+ 3293  
2 Σg 2196 12 Σg+ 2184  
3 Σg 904 30 Σg+ 874  
4 Σu 3370 41 Σu+ 3329  
5 Σu 2023 3 Σu+ 2020  
6 Πg 642 15 Πg 627  
7 Πg 544 62 Πg 482  
8 Πu 503 -127 Πu 630  
9 Πu 255 24 Πu 231  
The calculated vibrational frequencies were scaled by 0.9835

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.