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

Compare vibrational frequencies in CCCBDB for C4H4 (cyclobutadiene)

QCISD/3-21G

Frequency in cm-1
  Calculated   Experimental
Mode Number Symmetry Frequency diff Symmetry Frequency Comment
1 Ag 3150 10 Ag 3140 CH str
2 Ag 1459 -219 Ag 1678 C=C str
3 Ag 1075 16 Ag 1059 CH def
4 Ag 851 -138 Ag 989 CH def
5 Au 729        
6 Au 488        
7 B1g 797        
8 B1u 3134 10 B1u 3124 CH str
9 B1u 1472 -55 B1u 1527 C=C str
10 B1u 1025 -3 B1u 1028 CH def
11 B2g 563 32 B2g 531 CH OPLA
12 B2u 3114 9 B2u 3105 CH str
13 B2u 1230 -14 B2u 1244 CH def
14 B2u 597 -122 B2u 719 ring def
15 B3g 3101 8 B3g 3093 CH str
16 B3g 1162        
17 B3g 877        
18 B3u 589 13 B3u 576 CH OPLA
The calculated vibrational frequencies were scaled by 0.9692

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.