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Compare vibrational frequencies for two calculations for C6H4F2 (1,4-difluorobenzene)


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

scale factors=0.8985, 0.943 -0.515 0.302 -0.611 0.160
  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   3065 3084 -18.8 0.994   1.097 1.097 -0.000 1.000   0.00 0.00  
2 Ag Ag   1643 1595 47.8 1.030   6.039 6.554 0.921   0.00 0.00  
3 Ag Ag   1262 1239 23.0 1.019   10.646 10.344 1.029   0.00 0.00  
4 Ag Ag   1132 1121 11.3 1.010   1.123 1.110 0.013 1.012   0.00 0.00  
5 Ag Ag   841 828 12.6 1.015   6.629 6.632 -0.003 1.000   0.00 0.00  
6 Ag Ag   439 429 10.3 1.024   13.345 13.298 0.047 1.004   0.00 0.00  
7 Au Au   973 831 141.7 1.171   1.328 1.241 0.087 1.071   0.00 0.00  
8 Au Au   428 393 35.0 1.089   3.099 3.710 0.835   0.00 0.00  
9 B1g B1g   827 751 76.3 1.102   1.243 1.243 0.000 1.000   0.00 0.00  
10 B1u B1u   3051 3072 -20.7 0.993   1.090 1.090 0.001 1.001   8.18 2.88 2.841
11 B1u B1u   1527 1487 40.7 1.027   2.989 3.057 -0.068 0.978   286.17 246.01 1.163
12 B1u B1u   1226 1190 36.7 1.031   2.819 2.660 1.060   189.87 144.03 1.318
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.