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III.G.7. (XIII.B.3.) (XIII.D.5.)

Compare vibrational frequencies for two calculations for C2H5Br (Ethyl bromide)

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 A' A'   2967 3018 -50.8 0.983   1.060 1.099 -0.039 0.965   33.09 13.49 19.61 2.454
2 A' A'   2967 2988 -20.5 0.993   1.060 1.059 0.001 1.001   33.12 8.52 24.60 3.888
3 A' A'   2944 2933 10.7 1.004   1.094 1.038 0.056 1.054   10.55 13.27 -2.72 0.795
4 A' A'   2944 1473 1471.0 1.999   1.094 1.049 0.045 1.043   10.50 2.90 7.60 3.620
5 A' A'   2884 1462 1421.9 1.973   1.041 1.102 -0.061 0.945   28.52 1.24 27.28 23.071
6 A' A'   2884 1387 1496.2 2.079   1.041 1.240 -0.199 0.840   28.56 6.01 22.55 4.754
7 A' A'   1475 1255 220.3 1.175   1.056 1.267 -0.211 0.833   1.40 55.26 -53.85 0.025
8 A' A'   1475 1057 417.9 1.395   1.056 2.187 -1.132 0.483   1.40 0.23 1.17 6.198
9 A' A'   1471 955 516.2 1.541   1.102 1.633 -0.531 0.675   1.33 12.03 -10.70 0.111
10 A' A'   1471 560 911.2 2.627   1.102 4.045 -2.943 0.273   1.33 13.12 -11.78 0.102
11 A' A'   1406 282 1124.1 4.988   1.232 3.200 -1.968 0.385   2.44 1.99 0.45 1.228
12 A' A"   1406 3060 -1653.9 0.459   1.232 1.111 0.121 1.109   2.44 8.73 -6.29 0.279
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.