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# Compare vibrational frequencies for two calculations for CHOCH2OH (hydroxy acetaldehyde)

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

scale factors=0.8985, 0.943 1.373 -0.304
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'   3643 3468 175.3 1.051   1.066 1.065 0.001 1.001   88.62 66.43 1.334
2 A' A'   2878 2889 -10.9 0.996   1.079 1.065 0.014 1.013   105.13 63.38 1.659
3 A' A'   2856 2871 -14.1 0.995   1.069 1.081 -0.013 0.988   18.85 41.99 0.449
4 A' A'   1817 1677 139.7 1.083   10.060 8.687 1.158   189.49 70.12 2.702
5 A' A'   1480 1466 13.9 1.010   1.092 1.083 0.009 1.008   4.17 8.25 0.506
6 A' A'   1436 1407 29.1 1.021   1.427 1.341 0.086 1.064   74.20 88.61 0.837
7 A' A'   1380 1351 29.6 1.022   1.204 1.216 -0.012 0.990   18.99 11.56 1.642
8 A' A'   1273 1263 9.8 1.008   1.393 1.490 -0.097 0.935   71.54 54.59 1.310
9 A' A'   1126 1092 34.3 1.031   2.901 2.905 -0.003 0.999   89.49 68.34 1.309
10 A' A'   847 852 -4.4 0.995   3.061 3.078 -0.018 0.994   46.59 47.16 0.988
11 A' A'   737 728 8.0 1.011   4.919 5.223 0.942   22.71 10.19 2.229
12 A' A'   289 296 -7.0 0.976   6.580 6.632 -0.052 0.992   23.38 22.03 1.061
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.