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Compare vibrational frequencies for two calculations for SiCl3CH3 (methyltrichlorosilane)


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

scale factors=0.8985, 0.943 0.207 -0.132
  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   2883 2932 -48.4 0.984   1.035 1.035 0.000 1.000   0.43 0.78 0.559
2 A1 A1   1319 1299 20.1 1.015   1.237 1.246 -0.010 0.992   25.02 31.55 0.793
3 A1 A1   711 735 -24.7 0.966   5.439 5.232 1.040   84.81 80.20 1.057
4 A1 A1   425 436 -11.3 0.974   12.991 13.075 -0.084 0.994   26.29 21.39 1.229
5 A1 A1   225 226 -1.6 0.993   14.139 14.271 0.991   19.53 15.49 1.261
6 A2 A2   158 186 -28.7 0.846   1.016 1.016 -0.000 1.000   0.00 0.00  
7 E E   2958 3029 -71.0 0.977   1.102 1.102 0.000 1.000   3.12 0.25 12.346
8 E E   2958 3029 -71.0 0.977   1.102 1.102 0.000 1.000   3.12 0.25 12.346
9 E E   1431 1425 5.4 1.004   1.049 1.049 -0.000 1.000   4.33 4.87 0.888
10 E E   1431 1425 5.4 1.004   1.049 1.049 -0.000 1.000   4.33 4.87 0.888
11 E E   819 825 -6.2 0.992   1.361 1.381 -0.020 0.985   96.53 98.89 0.976
12 E E   819 825 -6.2 0.992   1.361 1.381 -0.020 0.985   96.53 98.89 0.976
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.