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

Compare vibrational frequencies for two calculations for C2H2N4 (sym-tetrazine)

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 Ag Ag   3097 3089 7.9 1.003   1.097 1.094 0.002 1.002   0.00 0.00 0.00  
2 Ag Ag   1557 1360 197.4 1.145   12.177 11.587 0.590 1.051   0.00 0.00 0.00  
3 Ag Ag   1058 957 101.4 1.106   8.759 9.051 -0.292 0.968   0.00 0.00 0.00  
4 Ag Ag   741 706 35.3 1.050   9.072 9.275 -0.204 0.978   0.00 0.00 0.00  
5 Au Au   405 319 86.7 1.272   14.003 14.003 0.000 1.000   0.00 0.00 0.00  
6 B1u B1u   3095 3089 6.5 1.002   1.096 1.095 0.001 1.001   9.27 4.51 4.75 2.054
7 B1u B1u   1240 1160 79.7 1.069   8.349 7.725 0.624 1.081   79.95 64.40 15.55 1.241
8 B1u B1u   1070 1043 26.3 1.025   11.300 12.857 -1.557 0.879   6.42 0.06 6.36 105.584
9 B2g B2g   991 924 66.9 1.072   1.332 1.246 0.086 1.069   0.00 0.00 0.00  
10 B2g B2g   807 753 53.3 1.071   5.590 7.725 -2.135 0.724   0.00 0.00 0.00  
11 B2u B2u   1480 1399 81.1 1.058   2.113 1.655 0.458 1.277   0.99 6.91 -5.92 0.143
12 B2u B2u   1145 1156 -11.4 0.990   1.748 4.158 -2.410 0.420   23.59 0.39 23.20 60.587
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.