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Compare vibrational frequencies for two calculations for C5H8O (Furan, 2,3-dihydro-5-methyl-)


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

scale factors=0.8985, 0.943 0.261
  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   3075 3109 -34.6 0.989   1.097 1.096 0.001 1.001   6.45 2.65 2.431
2 A A   2967 3033 -66.0 0.978   1.103 1.104 -0.000 1.000   23.27 10.35 2.250
3 A A   2962 3014 -51.9 0.983   1.108 1.104 0.003 1.003   62.30 30.36 2.052
4 A A   2937 3008 -70.3 0.977   1.102 1.102 0.000 1.000   22.00 9.53 2.308
5 A A   2917 2974 -56.8 0.981   1.068 1.099 -0.031 0.972   83.12 22.74 3.655
6 A A   2900 2932 -32.0 0.989   1.097 1.036 0.061 1.059   22.03 14.33 1.537
7 A A   2887 2927 -40.0 0.986   1.037 1.067 -0.029 0.973   26.62 43.84 0.607
8 A A   2875 2914 -39.2 0.987   1.065 1.066 -0.001 0.999   65.82 36.46 1.805
9 A A   1712 1655 57.2 1.035   7.294 7.033 1.037   80.45 32.85 2.449
10 A A   1511 1486 25.3 1.017   1.107 1.108 -0.001 0.999   0.54 0.16 3.398
11 A A   1485 1467 18.0 1.012   1.104 1.096 0.008 1.007   0.22 0.43 0.498
12 A A   1467 1465 2.0 1.001   1.068 1.071 -0.003 0.997   2.61 5.81 0.449
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.