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Compare vibrational frequencies for two calculations for C6H12 ((1r,3r)-1,3-dimethylcyclobutane)


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

scale factors=0.8985, 0.943 0.139 0.235
  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 Ag Ag   2921 2996 -75.6 0.975   1.101 1.103 -0.002 0.999   0.00 0.00  
2 Ag Ag   2900 2941 -41.1 0.986   1.076 1.086 -0.010 0.991   0.00 0.00  
3 Ag Ag   2883 2928 -44.6 0.985   1.074 1.062 0.012 1.011   0.00 0.00  
4 Ag Ag   2864 2913 -48.2 0.983   1.036 1.035 0.001 1.001   0.00 0.00  
5 Ag Ag   1481 1471 10.1 1.007   1.129 1.048 0.081 1.077   0.00 0.00  
6 Ag Ag   1474 1465 9.0 1.006   1.048 1.118 -0.071 0.937   0.00 0.00  
7 Ag Ag   1404 1380 24.3 1.018   1.322 1.303 0.019 1.015   0.00 0.00  
8 Ag Ag   1354 1334 19.9 1.015   1.381 1.459 -0.078 0.947   0.00 0.00  
9 Ag Ag   1228 1216 12.3 1.010   1.411 1.442 -0.031 0.978   0.00 0.00  
10 Ag Ag   1072 1094 -22.0 0.980   2.392 2.254 1.061   0.00 0.00  
11 Ag Ag   935 928 7.5 1.008   1.122 1.118 0.005 1.004   0.00 0.00  
12 Ag Ag   853 856 -3.6 0.996   3.739 3.504 1.067   0.00 0.00  
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.