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Compare vibrational frequencies for two calculations for C3H6O (Oxetane)


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

scale factors=0.8985, 0.943 0.910 -0.608 -0.270
  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   2927 2973 -46.4 0.984   1.063 1.061 0.002 1.002   26.03 18.74 1.390
2 A1 A1   2903 2927 -24.4 0.992   1.058 1.058 0.000 1.000   12.65 1.54 8.205
3 A1 A1   1531 1519 12.0 1.008   1.132 1.123 0.009 1.008   0.00 0.02 0.116
4 A1 A1   1474 1465 9.2 1.006   1.113 1.102 0.011 1.010   1.88 2.44 0.769
5 A1 A1   1379 1337 42.2 1.032   1.457 1.429 0.028 1.020   13.18 3.06 4.303
6 A1 A1   1028 1018 10.3 1.010   4.953 4.043 1.225   20.58 3.21 6.406
7 A1 A1   925 900 24.6 1.027   2.675 3.283 0.815   31.53 28.94 1.090
8 A1 A1   808 763 45.6 1.060   5.830 6.100 0.956   5.26 4.30 1.224
9 A2 A2   2937 2975 -38.8 0.987   1.112 1.112 0.000 1.000   0.00 0.00  
10 A2 A2   1212 1200 12.3 1.010   1.127 1.141 -0.015 0.987   0.00 0.00  
11 A2 A2   1145 1122 23.7 1.021   1.097 1.082 0.015 1.014   0.00 0.00  
12 A2 A2   815 819 -4.3 0.995   1.084 1.086 -0.002 0.998   0.00 0.00  
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.