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# Compare vibrational frequencies for two calculations for CH3NO2 (Methane, nitro-)

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

scale factors=0.8985, 0.943 12.061 -0.138 -11.573 0.110 0.641 -1.043 -0.455 -1.796
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'   3027 3075 -47.8 0.984   1.104 1.106 -0.002 0.998   2.50 1.20 2.081
2 A' A'   2940 2972 -31.8 0.989   1.033 1.030 0.003 1.002   1.93 1.25 1.542
3 A' A'   1517 1448 69.3 1.048   13.112 1.052 12.470   103.97 10.80 9.625
4 A' A'   1456 1381 74.6 1.054   1.055 1.193 0.884   11.33 0.89 12.716
5 A' A'   1411 1353 57.9 1.043   1.195 12.768 0.094   0.12 59.39 0.002
6 A' A'   1142 1105 37.6 1.034   1.586 1.476 1.075   1.99 0.37 5.378
7 A' A'   945 889 55.6 1.063   8.875 8.234 1.078   4.82 5.67 0.849
8 A' A'   669 634 34.7 1.055   5.748 6.791 0.846   42.03 27.34 1.537
9 A' A'   620 566 54.2 1.096   3.384 3.838 0.882   15.75 4.17 3.780
10 A" A"   3059 3099 -39.9 0.987   1.112 1.111 0.002 1.002   1.03 0.08 12.390
11 A" A"   1689 1712 -22.5 0.987   9.990 11.786 0.848   582.81 83.76 6.958
12 A" A"   1444 1443 1.3 1.001   1.059 1.055 0.004 1.004   37.84 19.18 1.973
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.