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Compare vibrational frequencies for two calculations for HNO2+ (nitrous acid cation)


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

scale factors=0.8985, 0.943 -9.907 4.102 7.902 2.622
  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'   3425 3225 200.4 1.062   1.070 1.086 -0.016 0.986   510.07 184.18 2.769
2 A' A'   1403 2882 -1478.6 0.487   1.298 11.205 0.116   114.83 3042.18 0.038
3 A' A'   1303 1242 61.3 1.049   5.439 1.337 4.069   102.23 282.46 0.362
4 A' A'   1149 1110 39.2 1.035   14.399 6.497 2.216   203.16 27.41 7.413
5 A' A'   400 672 -271.6 0.596   8.839 6.217 1.422   15.99 6.32 2.530
6 A" A"   689 502 186.6 1.371   1.179 1.269 -0.089 0.929   157.55 159.32 0.989
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.