Halon Thermochemistry: Ab Initio Calculations of the Enthalpies of Formation of Fluoromethanes.
Halon Thermochemistry: Ab Initio Calculations of the
Enthalpies of Formation of Fluoromethanes.
Berry, R. J.; Burgess, D. R. F., Jr.; Nyden, M. R.;
Zachariah, M. R.
Journal of Physical Chemistry, Vol. 99, No. 47,
halons; thermochemistry; enthalpy
Atomic equivalent (AEQ), BAC-MP4, G2(MP2), G2, CBS-4,
BCS-Q, and CBS-QCI/APNO molecular orbital calculations
were used to calculate enthalpies of formation in the
series of fluoromethanes, CHxF4-x, x = 0-4. While the
computed BAC-MP4 and CBS-4 were in close agreement with
experiment, errors in enthalpies from the other five
methods were relatively high. In particular, enthalpies
of formation calculated with the G2(MP2) and G2
procedures exhibited systematic deviations from
experiment which were linearly dependent upon the number
of C-F bonds in the molecule. Application of isodesmic
reaction calculaitons yielded values of G2(MP2), G2,
CBS-Q, and CBS-QCI/APNO that were in remarkably close
agreement with experiment. This technique had no
significant effect on the quality of results from the
AEQ, BAC-MP4, and CBS-4 methods.