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III.G.7. (XIII.B.3.) (XIII.D.5.)

Compare vibrational frequencies for two calculations for Fe(CO)5 (Iron pentacarbonyl)

A = HF/6-31G*

B = MP2/6-31G*

scale factors=0.8985, 0.943
  symmetry   frequency (cm-1)   reduced mass (amu)   IR Intensity (km mol-1)
mode number A B   A B diff. ratio   A B diff. ratio   A B diff. ratio
1 A1 A1   2198 1996 202.4 1.101   13.427 13.142 0.285 1.022   664.23 351.82 312.41 1.888
2 A1 A1   2143 1800 343.6 1.191   13.403 13.187 0.216 1.016   253.63 495.38 -241.75 0.512
3 A1 A1   443 741 -298.2 0.598   15.895 15.536 0.358 1.023   119.10 98.82 20.28 1.205
4 A1 A1   332 595 -263.3 0.558   16.088 16.627 -0.538 0.968   31.94 81.33 -49.38 0.393
5 A1 A1   235 561 -325.3 0.420   14.108 14.240 -0.132 0.991   42.05 146.56 -104.50 0.287
6 A1 A1   89 92 -2.9 0.969   18.434 19.002 -0.568 0.970   0.02 0.45 -0.43 0.041
7 A2 A2   258 461 -202.3 0.561   12.744 12.666 0.079 1.006   0.00 0.00 0.00  
8 B1 B1   465 614 -148.5 0.758   12.215 12.275 -0.060 0.995   0.00 0.00 0.00  
9 B1 B1   88 104 -15.8 0.847   15.629 15.531 0.097 1.006   0.00 0.00 0.00  
10 B2 B2   2070 2033 37.4 1.018   13.433 13.067 0.366 1.028   0.00 0.00 0.00  
11 B2 B2   354 621 -267.7 0.569   13.129 14.291 -1.162 0.919   0.00 0.00 0.00  
12 B2 B2   178 292 -114.2 0.610   13.535 14.269 -0.734 0.949   0.00 0.00 0.00  
scaled by     0.8985 0.943

See section III.C.1 List or set vibrational scaling factors to change the scale factors used here.
See section III.C.2 Calculate a vibrational scaling factor for a given set of molecules to determine the least squares best scaling factor.