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

Compare vibrational frequencies for two calculations for H2OCH3OCH3 (water dimethylether dimer)

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   3740 3655 85.1 1.023   1.080 1.076 0.003 1.003   133.56 105.85 27.71 1.262
2 A A   3626 3494 131.4 1.038   1.049 1.050 -0.002 0.998   185.14 231.13 -45.99 0.801
3 A A   2987 3057 -69.8 0.977   1.100 1.102 -0.002 0.999   29.33 10.78 18.54 2.720
4 A A   2976 3041 -65.0 0.979   1.100 1.102 -0.002 0.998   42.01 20.48 21.54 2.052
5 A A   2912 2971 -58.6 0.980   1.106 1.108 -0.002 0.998   132.60 13.70 118.90 9.680
6 A A   2910 2964 -54.2 0.982   1.107 1.106 0.000 1.000   15.99 82.31 -66.32 0.194
7 A A   2870 2901 -31.2 0.989   1.037 1.035 0.002 1.002   63.02 45.36 17.67 1.389
8 A A   2858 2894 -36.7 0.987   1.035 1.033 0.002 1.001   46.38 39.30 7.08 1.180
9 A A   1662 1665 -2.3 0.999   1.079 1.078 0.001 1.001   97.12 73.44 23.68 1.323
10 A A   1499 1488 10.6 1.007   1.091 1.061 0.030 1.029   0.24 0.97 -0.73 0.245
11 A A   1484 1474 10.3 1.007   1.058 1.054 0.004 1.003   7.93 11.90 -3.98 0.666
12 A A   1483 1469 14.4 1.010   1.060 1.055 0.004 1.004   9.06 13.11 -4.06 0.691
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.