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Compare vibrational frequencies for two calculations for C2H4CO3 (Ethylene carbonate)


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

scale factors=0.8985, 0.943 -3.167 0.370 0.282 0.108
  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 2967 -40.3 0.986   1.060 1.059 0.000 1.000   60.16 35.10 1.714
2 A1 A1   1910 1818 92.1 1.051   12.976 12.915 0.061 1.005   822.50 536.83 1.532
3 A1 A1   1535 1510 25.1 1.017   1.095 1.091 0.004 1.004   8.21 1.45 5.673
4 A1 A1   1397 1342 55.3 1.041   1.406 1.356 0.050 1.037   7.03 0.21 34.275
5 A1 A1   1232 1080 151.9 1.141   7.788 10.955 0.711   317.84 214.63 1.481
6 A1 A1   922 952 -29.8 0.969   2.865 2.854 0.011 1.004   16.43 31.49 0.522
7 A1 A1   835 844 -9.1 0.989   10.417 10.047 1.037   32.95 4.14 7.969
8 A1 A1   711 683 27.1 1.040   12.169 11.886 1.024   1.70 1.40 1.215
9 A2 A2   2947 3013 -66.6 0.978   1.113 1.115 -0.002 0.999   0.00 0.00  
10 A2 A2   1240 1202 38.2 1.032   1.042 1.093 -0.051 0.954   0.00 0.00  
11 A2 A2   1161 1117 43.3 1.039   1.631 1.523 1.071   0.00 0.00  
12 A2 A2   167i 144i -22.6 1.157   2.204 2.197 0.007 1.003   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.