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Compare vibrational frequencies for two calculations for HCNH (HCNH)


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

scale factors=0.8985, 0.943 -0.173 2.691 0.219 -0.126
  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 A' A'   3219 3248 -28.5 0.991   1.075 1.100 -0.026 0.977   2.51 18.07 0.139
2 A' A'   2919 2885 34.2 1.012   1.088 1.261 0.863   33.03 323.74 0.102
3 A' A'   1497 2339 -841.4 0.640   6.433 3.742 1.719   0.67 390.15 0.002
4 A' A'   1137 985 151.9 1.154   1.474 1.256 1.174   116.70 89.89 1.298
5 A' A'   910 699 210.3 1.301   1.045 1.172 0.892   45.48 332.42 0.137
6 A" A"   955 896 59.9 1.067   1.285 1.335 -0.050 0.962   8.56 12.02 0.713
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.