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Compare vibrational frequencies for two calculations for C2H5+ (Ethyl cation)


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 A1 A1   3004 3028 -24.2 0.992   1.068 1.068 0.000 1.000   0.33 0.02 19.292
2 A1 A1   2066 2130 -63.4 0.970   1.066 1.068 -0.002 0.998   24.29 49.30 0.493
3 A1 A1   1548 1526 22.4 1.015   1.774 1.752 0.022 1.013   12.04 8.59 1.401
4 A1 A1   1313 1322 -8.3 0.994   1.676 1.705 -0.028 0.983   19.76 13.27 1.490
5 A1 A1   1132 1111 21.5 1.019   1.163 1.157 0.006 1.005   65.14 72.51 0.898
6 A2 A2   3096 3129 -32.9 0.989   1.130 1.129 0.001 1.001   0.00 0.00  
7 A2 A2   1223 1216 7.3 1.006   1.466 1.464 0.002 1.002   0.00 0.00  
8 A2 A2   1045 1047 -1.8 0.998   1.008 1.011 -0.003 0.997   0.00 0.00  
9 B1 B1   3110 3143 -33.0 0.989   1.121 1.120 0.000 1.000   56.05 65.32 0.858
10 B1 B1   1164 1105 59.1 1.053   1.041 1.045 -0.004 0.996   11.72 19.78 0.593
11 B1 B1   818 818 0.5 1.001   1.028 1.025 0.003 1.003   0.77 0.66 1.160
12 B2 B2   2998 3025 -27.1 0.991   1.048 1.048 0.000 1.000   24.79 33.96 0.730
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.