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

Compare vibrational frequencies for two calculations for CH6N3+ (guanidinium)

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 A1' A1'   3444 3431 13.6 1.004   1.052 1.052 0.000 1.000   0.00 0.00 0.00  
2 A1' A1'   1678 1641 37.3 1.023   1.135 1.137 -0.002 0.998   0.00 0.00 0.00  
3 A1' A1'   992 990 2.3 1.002   4.469 4.433 0.036 1.008   0.00 0.00 0.00  
4 A1" A1"   82 230i 312.5 -0.358   1.008 1.008 0.000 1.000   0.00 0.00 0.00  
5 A2' A2'   3532 3525 6.9 1.002   1.107 1.106 0.001 1.001   0.00 0.00 0.00  
6 A2' A2'   1016 985 31.7 1.032   1.180 1.182 -0.002 0.998   0.00 0.00 0.00  
7 A2" A2"   716 653 63.1 1.097   9.426 4.631 4.795 2.035   33.29 14.76 18.53 2.255
8 A2" A2"   465 371 94.0 1.253   1.144 1.308 -0.164 0.874   1078.61 994.96 83.65 1.084
9 E' E'   3538 3530 7.8 1.002   1.109 1.108 0.002 1.001   223.86 211.43 12.42 1.059
10 E' E'   3538 3530 7.8 1.002   1.109 1.108 0.002 1.001   223.86 211.43 12.42 1.059
11 E' E'   3426 3413 13.7 1.004   1.047 1.047 0.000 1.000   239.52 271.77 -32.25 0.881
12 E' E'   3426 3413 13.7 1.004   1.047 1.047 0.000 1.000   239.52 271.77 -32.25 0.881
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.