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

Compare vibrational frequencies for two calculations for C6H12 (Cyclohexane)

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 A1g A1g   2904 2956 -52.6 0.982   1.087 1.098 -0.011 0.990   0.00 0.00 0.00  
2 A1g A1g   2861 2908 -47.1 0.984   1.080 1.068 0.012 1.011   0.00 0.00 0.00  
3 A1g A1g   1494 1483 11.2 1.008   1.104 1.103 0.002 1.002   0.00 0.00 0.00  
4 A1g A1g   1166 1155 10.7 1.009   2.182 2.231 -0.049 0.978   0.00 0.00 0.00  
5 A1g A1g   767 791 -24.1 0.970   3.505 3.468 0.037 1.011   0.00 0.00 0.00  
6 A1g A1g   362 374 -12.4 0.967   1.563 1.551 0.012 1.007   0.00 0.00 0.00  
7 A1u A1u   1367 1342 24.6 1.018   1.407 1.441 -0.034 0.977   0.00 0.00 0.00  
8 A1u A1u   1114 1101 13.6 1.012   1.172 1.645 -0.473 0.712   0.00 0.00 0.00  
9 A1u A1u   1060 1085 -25.0 0.977   1.984 1.305 0.679 1.520   0.00 0.00 0.00  
10 A2g A2g   1330 1304 26.1 1.020   1.303 1.305 -0.001 0.999   0.00 0.00 0.00  
11 A2g A2g   1042 1037 5.2 1.005   1.011 1.011 -0.000 1.000   0.00 0.00 0.00  
12 A2u A2u   2911 2969 -58.5 0.980   1.106 1.106 0.000 1.000   211.47 113.07 98.40 1.870
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.