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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 3124 -16 Ag 3140 CH str
2 Ag 1447 -231 Ag 1678 C=C str
3 Ag 1066 7 Ag 1059 CH def
4 Ag 844 -145 Ag 989 CH def
5 Au 723        
6 Au 484        
7 B1g 790        
8 B1u 3107 -17 B1u 3124 CH str
9 B1u 1460 -67 B1u 1527 C=C str
10 B1u 1016 -12 B1u 1028 CH def
11 B2g 559 28 B2g 531 CH OPLA
12 B2u 3088 -17 B2u 3105 CH str
13 B2u 1220 -24 B2u 1244 CH def
14 B2u 592 -127 B2u 719 ring def
15 B3g 3075 -18 B3g 3093 CH str
16 B3g 1152        
17 B3g 870        
18 B3u 585 9 B3u 576 CH OPLA
The calculated vibrational frequencies were scaled by 0.9611

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.