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

Compare vibrational frequencies for two calculations for C4H8O (Cyclobutanol)

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 A' A   3682 3541 141.4 1.040   1.067 1.066 0.001 1.001   29.37 16.46 12.91 1.784
2 A' A   2961 3021 -60.1 0.980   1.105 1.109 -0.004 0.997   117.78 42.69 75.09 2.759
3 A' A   2948 3005 -56.5 0.981   1.099 1.106 -0.007 0.993   11.99 17.04 -5.04 0.704
4 A' A   2929 2969 -39.2 0.987   1.091 1.087 0.004 1.003   10.81 15.74 -4.93 0.687
5 A' A   2908 2958 -49.2 0.983   1.066 1.061 0.005 1.005   33.52 23.66 9.85 1.416
6 A' A   2888 2935 -46.6 0.984   1.068 1.064 0.004 1.004   33.54 14.06 19.48 2.385
7 A' A   1498 1485 12.9 1.009   1.168 1.151 0.017 1.015   8.86 5.39 3.47 1.644
8 A' A   1468 1463 4.8 1.003   1.092 1.084 0.008 1.007   3.58 6.54 -2.96 0.548
9 A' A   1422 1387 34.5 1.025   1.311 1.252 0.059 1.047   94.64 67.27 27.37 1.407
10 A' A   1310 1294 16.6 1.013   1.545 1.535 0.010 1.006   1.41 1.80 -0.39 0.784
11 A' A   1265 1230 35.1 1.028   1.479 1.594 -0.115 0.928   14.39 25.04 -10.65 0.575
12 A' A   1195 1181 13.7 1.012   1.432 1.430 0.002 1.001   0.31 0.04 0.27 7.333
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.