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Compare vibrational frequencies for two calculations for C2H2N4 (sym-tetrazine)


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

scale factors=0.8985, 0.943 0.590 -0.292 -0.204 0.624 -1.555 -2.136 0.458 -2.412
  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 Ag Ag   3097 3089 7.9 1.003   1.097 1.094 0.002 1.002   0.00 0.00  
2 Ag Ag   1557 1360 197.4 1.145   12.177 11.587 1.051   0.00 0.00  
3 Ag Ag   1058 957 101.4 1.106   8.759 9.051 0.968   0.00 0.00  
4 Ag Ag   741 706 35.3 1.050   9.072 9.275 0.978   0.00 0.00  
5 Au Au   405 319 86.7 1.272   14.003 14.003 0.000 1.000   0.00 0.00  
6 B1u B1u   3095 3089 6.5 1.002   1.096 1.095 0.001 1.001   9.27 4.52 2.050
7 B1u B1u   1240 1160 79.7 1.069   8.349 7.725 1.081   79.95 64.42 1.241
8 B1u B1u   1070 1043 26.3 1.025   11.300 12.855 0.879   6.42 0.06 110.491
9 B2g B2g   991 924 66.9 1.072   1.332 1.246 0.086 1.069   0.00 0.00  
10 B2g B2g   807 753 53.3 1.071   5.590 7.726 0.724   0.00 0.00  
11 B2u B2u   1480 1399 81.2 1.058   2.113 1.655 1.277   0.99 6.91 0.143
12 B2u B2u   1145 1156 -11.6 0.990   1.748 4.160 0.420   23.59 0.39 61.010
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.