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

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

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'   2984 3022 -38.1 0.987   1.062 1.060 0.002 1.002   12.66 5.36 7.30 2.363
2 A' A'   2959 3017 -58.8 0.981   1.109 1.110 -0.000 1.000   75.02 35.47 39.55 2.115
3 A' A'   2932 2989 -57.1 0.981   1.102 1.107 -0.006 0.995   23.83 12.65 11.18 1.884
4 A' A'   2912 2955 -42.6 0.986   1.066 1.060 0.006 1.006   49.34 34.97 14.37 1.411
5 A' A'   2892 2932 -40.3 0.986   1.063 1.061 0.002 1.002   14.94 8.46 6.48 1.766
6 A' A'   1721 1674 47.6 1.028   6.363 6.662 -0.299 0.955   18.87 9.29 9.58 2.031
7 A' A'   1485 1474 11.0 1.007   1.131 1.126 0.006 1.005   0.30 0.02 0.28 16.107
8 A' A'   1455 1450 5.6 1.004   1.094 1.089 0.005 1.005   1.15 2.47 -1.32 0.466
9 A' A'   1418 1399 19.3 1.014   1.165 1.156 0.008 1.007   0.64 0.68 -0.03 0.955
10 A' A'   1263 1224 39.6 1.032   1.477 1.492 -0.015 0.990   3.82 0.17 3.65 22.549
11 A' A'   1204 1181 23.5 1.020   1.282 1.334 -0.052 0.961   0.18 0.00 0.18 72.120
12 A' A'   1086 1057 28.6 1.027   2.006 1.896 0.109 1.058   0.19 0.28 -0.09 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.