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Compare vibrational frequencies for two calculations for C4H8O2 (1,3-Dioxolane, 2-methyl-)


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   2974 3047 -73.0 0.976   1.099 1.105 -0.006 0.995   55.05 12.32 4.470
2 A A   2968 3037 -68.7 0.977   1.105 1.104 0.001 1.001   35.41 10.21 3.468
3 A A   2959 3020 -61.0 0.980   1.104 1.101 0.003 1.003   28.58 23.83 1.200
4 A A   2945 2989 -44.0 0.985   1.106 1.108 -0.002 0.998   58.97 33.02 1.786
5 A A   2905 2945 -40.3 0.986   1.061 1.035 0.027 1.026   57.01 5.87 9.714
6 A A   2896 2930 -33.9 0.988   1.037 1.060 -0.023 0.978   19.46 47.79 0.407
7 A A   2878 2905 -27.0 0.991   1.073 1.069 0.003 1.003   76.62 44.02 1.740
8 A A   2855 2855 -0.7 1.000   1.084 1.086 -0.002 0.999   86.73 83.21 1.042
9 A A   1519 1498 21.2 1.014   1.118 1.106 0.012 1.011   0.39 0.31 1.251
10 A A   1502 1479 23.3 1.016   1.107 1.105 0.002 1.002   1.52 2.82 0.539
11 A A   1467 1461 6.1 1.004   1.087 1.051 0.036 1.035   11.17 4.21 2.652
12 A A   1466 1458 7.6 1.005   1.066 1.051 0.015 1.014   4.87 2.04 2.389
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.