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

Compare vibrational frequencies for two calculations for HCN+ (hydrogen cyanide cation)

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 Σ Σ   3073 3745 -672.0 0.821   1.170 4.269 -3.100 0.274   261.48 1.27 260.21 205.924
2 Σ Σ   1872 2789 -917.0 0.671   5.529 1.247 4.282 4.432   47.81 336.76 -288.95 0.142
3 Π Π   784 911 -127.6 0.860   1.337 1.339 -0.001 0.999   51.94 36.08 15.87 1.440
4 Π Π   725 420 305.8 1.729   1.337 1.339 -0.001 0.999   4.51 0.15 4.36 29.212
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.