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

Compare vibrational frequencies for two calculations for C4H8 (cyclobutane)

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 A1 A1   2928 2992 -64.5 0.978   1.098 1.109 -0.011 0.990   0.00 0.00 0.00  
2 A1 A1   2905 2949 -44.5 0.985   1.077 1.066 0.012 1.011   0.00 0.00 0.00  
3 A1 A1   1506 1496 9.1 1.006   1.146 1.145 0.002 1.002   0.00 0.00 0.00  
4 A1 A1   1163 1151 11.1 1.010   2.028 2.032 -0.005 0.998   0.00 0.00 0.00  
5 A1 A1   972 1004 -31.9 0.968   3.812 3.760 0.052 1.014   0.00 0.00 0.00  
6 A1 A1   181 240 -58.4 0.756   1.496 1.507 -0.010 0.993   0.00 0.00 0.00  
7 A2 A2   1250 1213 36.9 1.030   1.381 1.383 -0.002 0.999   0.00 0.00 0.00  
8 A2 A2   940 930 9.2 1.010   1.008 1.008 0.000 1.000   0.00 0.00 0.00  
9 B1 B1   1254 1228 25.9 1.021   1.210 1.168 0.042 1.036   0.00 0.00 0.00  
10 B1 B1   1159 1132 27.7 1.025   1.195 1.261 -0.066 0.947   0.00 0.00 0.00  
11 B1 B1   914 927 -13.0 0.986   2.473 2.390 0.083 1.035   0.00 0.00 0.00  
12 B2 B2   2956 3017 -61.3 0.980   1.108 1.108 -0.000 1.000   148.87 77.28 71.59 1.926
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.