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Compare vibrational frequencies for two calculations for CH3CHOH+ (acetaldehyde, protonated)


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

scale factors=0.8985, 0.943 0.193 0.166 -0.328 0.252
  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'   3530 3365 164.7 1.049   1.069 1.069 0.000 1.000   395.12 346.42 1.141
2 A' A'   3025 3069 -43.5 0.986   1.097 1.104 -0.006 0.994   2.00 17.43 0.114
3 A' A'   3012 3033 -20.9 0.993   1.105 1.098 0.007 1.006   5.63 0.38 15.005
4 A' A'   2869 2903 -33.3 0.989   1.039 1.040 -0.001 0.999   27.14 60.64 0.448
5 A' A'   1630 1606 23.7 1.015   3.733 3.540 1.055   181.20 118.48 1.529
6 A' A'   1412 1400 12.1 1.009   1.331 1.165 1.143   69.88 25.66 2.723
7 A' A'   1409 1392 16.9 1.012   1.351 1.679 0.805   49.51 59.18 0.837
8 A' A'   1355 1330 25.2 1.019   1.209 1.222 -0.013 0.989   160.64 156.91 1.024
9 A' A'   1252 1256 -3.4 0.997   1.216 1.251 -0.035 0.972   50.84 61.10 0.832
10 A' A'   1069 1067 1.6 1.001   1.407 1.438 -0.031 0.978   49.67 64.10 0.775
11 A' A'   870 900 -29.9 0.967   2.120 1.868 1.135   15.78 24.66 0.640
12 A' A'   464 468 -3.2 0.993   2.490 2.454 0.036 1.015   16.04 15.62 1.027
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.