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

Compare vibrational frequencies for two calculations for C2H5 (Ethyl radical)

A = HF/6-31G*

B = MP2FC/6-31G*

  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   3004 3029 -25.0 0.992   1.068 1.068 0.000 1.000   0.33 0.02 0.31 21.993
2 A1 A1   2066 2129 -62.8 0.970   1.066 1.068 -0.002 0.998   24.29 49.25 -24.96 0.493
3 A1 A1   1548 1525 22.9 1.015   1.774 1.749 0.025 1.014   12.04 8.57 3.47 1.404
4 A1 A1   1313 1321 -7.9 0.994   1.676 1.707 -0.031 0.982   19.76 13.30 6.47 1.486
5 A1 A1   1132 1110 21.8 1.020   1.163 1.157 0.006 1.005   65.14 72.51 -7.37 0.898
6 A2 A2   3096 3130 -33.9 0.989   1.130 1.129 0.001 1.001   0.00 0.00 0.00  
7 A2 A2   1223 1216 7.3 1.006   1.466 1.464 0.003 1.002   0.00 0.00 0.00  
8 A2 A2   1045 1047 -1.5 0.999   1.008 1.011 -0.003 0.997   0.00 0.00 0.00  
9 B1 B1   3110 3144 -34.0 0.989   1.121 1.120 0.000 1.000   56.05 65.37 -9.32 0.857
10 B1 B1   1164 1106 58.8 1.053   1.041 1.045 -0.004 0.996   11.72 19.75 -8.03 0.594
11 B1 B1   818 817 0.9 1.001   1.028 1.025 0.003 1.003   0.77 0.66 0.11 1.164
12 B2 B2   2998 3026 -27.9 0.991   1.048 1.048 0.000 1.000   24.79 33.94 -9.15 0.730
13 B2 B2   1443 1434 8.7 1.006   1.104 1.105 -0.001 0.999   23.44 25.64 -2.20 0.914
14 B2 B2   1304 1287 17.4 1.014   1.171 1.121 0.050 1.044   17.71 13.75 3.96 1.288
15 B2 B2   385 716 -331.5 0.537   1.351 1.421 -0.070 0.951   321.96 144.04 177.93 2.235
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.