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Compare vibrational frequencies for two calculations for NaCN (Sodium Cyanide)


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   2205 1945 259.7 1.134   12.826 12.819 0.007 1.001   0.26 14.77 0.018
2 Σ Σ   331 341 -9.9 0.971   16.936 16.949 -0.012 0.999   63.79 55.81 1.143
3 Π Π   113 102 11.3 1.111   12.729 12.733 -0.004 1.000   15.26 18.48 0.826
4 Π Π   113 102 11.3 1.111   12.729 12.733 -0.004 1.000   15.26 18.48 0.826
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.