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Compare vibrational frequencies for two calculations for C5H8 (Cyclobutane, methylene-)


A = HF/6-31G*
B = MP2/6-31G*

scale factors=0.8985, 0.943 -0.299 0.109
  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'   2984 3022 -38.1 0.987   1.062 1.060 0.002 1.002   12.66 5.36 2.363
2 A' A'   2959 3017 -58.8 0.981   1.109 1.110 -0.000 1.000   75.02 35.47 2.115
3 A' A'   2932 2989 -57.1 0.981   1.102 1.107 -0.006 0.995   23.83 12.65 1.884
4 A' A'   2912 2955 -42.6 0.986   1.066 1.060 0.006 1.006   49.34 34.97 1.411
5 A' A'   2892 2932 -40.3 0.986   1.063 1.061 0.002 1.002   14.94 8.46 1.766
6 A' A'   1721 1674 47.6 1.028   6.363 6.662 0.955   18.87 9.29 2.031
7 A' A'   1485 1474 11.0 1.007   1.131 1.126 0.006 1.005   0.30 0.02 16.107
8 A' A'   1455 1450 5.6 1.004   1.094 1.089 0.005 1.005   1.15 2.47 0.466
9 A' A'   1418 1399 19.3 1.014   1.165 1.156 0.008 1.007   0.64 0.68 0.955
10 A' A'   1263 1224 39.6 1.032   1.477 1.492 -0.015 0.990   3.82 0.17 22.549
11 A' A'   1204 1181 23.5 1.020   1.282 1.334 -0.052 0.961   0.18 0.00 72.120
12 A' A'   1086 1057 28.6 1.027   2.006 1.896 1.058   0.19 0.28 0.685
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.