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Compare vibrational frequencies for two calculations for C6H12 (3-methylenepentane)


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

scale factors=0.8985, 0.943 -0.102
  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   2987 3019 -32.2 0.989   1.063 1.066 -0.003 0.997   16.15 19.95 0.810
2 A A   2945 3018 -72.5 0.976   1.104 1.098 0.006 1.006   71.20 15.35 4.638
3 A A   2935 3011 -76.2 0.975   1.103 1.103 -0.000 1.000   13.85 5.93 2.335
4 A A   2911 2964 -52.4 0.982   1.098 1.103 -0.005 0.995   6.59 15.12 0.436
5 A A   2884 2929 -44.9 0.985   1.050 1.036 0.014 1.014   29.19 17.63 1.655
6 A A   2874 2918 -43.5 0.985   1.052 1.061 -0.009 0.992   3.10 0.00 3446.778
7 A A   1685 1634 51.3 1.031   4.884 4.986 0.980   16.13 5.71 2.822
8 A A   1492 1486 6.5 1.004   1.087 1.072 0.015 1.014   0.02 0.86 0.027
9 A A   1479 1477 1.9 1.001   1.043 1.044 -0.000 1.000   3.29 4.43 0.744
10 A A   1469 1458 10.8 1.007   1.063 1.070 -0.007 0.994   5.38 3.94 1.365
11 A A   1435 1414 21.7 1.015   1.187 1.196 -0.008 0.993   0.95 2.03 0.468
12 A A   1401 1382 19.4 1.014   1.234 1.230 0.003 1.003   0.38 1.54 0.246
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.