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

Compare vibrational frequencies in CCCBDB for C4H4 (cyclobutadiene)

AM1

Frequency in cm-1
  Calculated   Experimental
Mode Number Symmetry Frequency diff Symmetry Frequency Comment
1   -3140 Ag 3140 CH str
2   -1678 Ag 1678 C=C str
3   -1059 Ag 1059 CH def
4   -989 Ag 989 CH def
         
8   -3124 B1u 3124 CH str
9   -1527 B1u 1527 C=C str
10   -1028 B1u 1028 CH def
11   -531 B2g 531 CH OPLA
12   -3105 B2u 3105 CH str
13   -1244 B2u 1244 CH def
14   -719 B2u 719 ring def
15   -3093 B3g 3093 CH str
         
18   -576 B3u 576 CH OPLA
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.