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Compare vibrational frequencies for two calculations for SiH4+ (Silane 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 A1 A1   2264 2292 -27.9 0.988   1.026 1.026 0.000 1.000   3.21 0.43 7.492
2 A1 A1   1782 1866 -84.4 0.955   1.059 1.058 0.002 1.001   24.16 10.10 2.391
3 A1 A1   962 949 13.3 1.014   1.017 1.022 -0.005 0.995   34.61 39.79 0.870
4 A1 A1   743 641 102.4 1.160   1.056 1.053 0.004 1.004   56.89 14.90 3.818
5 A2 A2   649 679 -30.6 0.955   1.008 1.008 0.000 1.000   0.00 0.00  
6 B1 B1   1239 1489 -250.0 0.832   1.009 1.010 -0.000 1.000   434.64 211.02 2.060
7 B1 B1   182i 483 -664.9 -0.376   1.135 1.133 0.002 1.002   95.33 2.50 38.166
8 B2 B2   2308 2345 -37.5 0.984   1.062 1.063 -0.001 0.999   9.02 1.13 8.011
9 B2 B2   770 781 -11.0 0.986   1.077 1.075 0.002 1.002   45.60 32.75 1.393
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.