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

Compare vibrational frequencies in CCCBDB for C2H2O2 (Ethanedial)

PBEPBE/3-21G*

Frequency in cm-1
  Calculated   Experimental
Mode Number Symmetry Frequency diff Symmetry Frequency Comment
1 Ag 2727 -116 Ag 2843  
2 Ag 1581 -164 Ag 1745  
3 Ag 1287 -51 Ag 1338  
4 Ag 935 -130 Ag 1065  
5 Ag 502 -49 Ag 551  
6 Au 794 -7 Au 801  
7 Au 187 60 Au 127  
8 Bg 1026 -22 Bg 1048  
9 Bu 2724 -111 Bu 2835  
10 Bu 1580 -152 Bu 1732  
11 Bu 1244 -68 Bu 1312  
12 Bu 284 -55 Bu 339  
The calculated vibrational frequencies were scaled by 0.9535

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.