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IV.A.5. Compare Barriers to Internal Rotation for C2F6 (hexafluoroethane)

Experimental barrier to internal rotation is 16.6 kJ/mol
Experimental data from JANAF
V3=16.6 +- 3 kJ mol-1, Ired = 7.32E-39 gm cm2
Energy Differences (Calculated - Experimental) in kJ/mol
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Methods with predefined basis sets
semi-empirical AM1 -15.9
PM3 -8.6

Methods with standard basis sets
3-21G 6-31G* 6-31+G** cc-pVTZ
hartree fock HF -2.8 -0.1 1.1 1.6
density functional B3LYP     -2.6  
3-21G 6-31G* 6-31+G** cc-pVTZ
Moller Plesset perturbation MP2 -3.8 -0.6 2.7  
3-21G 6-31G* 6-31+G** cc-pVTZ
For descriptions of the methods (AM1, HF, MP2, ...) and basis sets (3-21G, 3-21G*, 6-31G, ...) see the glossary in section I.C. Predefined means the basis set used is determined by the method.

References

squib reference
JANAF Chase, M.W., Jr.; Davies, C.A.; Downey, J.R., Jr.; Frurip, D.J.; McDonald, R.A.; Syverud, A.N., JANAF Thermochemical Tables (Third Edition), J. Phys. Chem. Ref. Data,Suppl. 1, 1985, 14, 1.

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