Rj. Berry et al., HALON THERMOCHEMISTRY - AB-INITIO CALCULATIONS OF THE ENTHALPIES OF FORMATION OF FLUOROMETHANES, Journal of physical chemistry, 99(47), 1995, pp. 17145-17150
Atomic equivalent (AEQ), BAC-MP4, G2(MP2), G2, CBS-4, CBS-Q, and CBS-Q
CI/APNO molecular orbital calculations were used to calculate enthalpi
es of formation in the series of fluoromethanes, CHxF4-x, x = 0-4. Whi
le the computed Delta(f)H degrees(BAC-MP4) and Delta(f)H degrees(CBS-4
) were in close agreement with experiment, errors in enthalpies from t
he other five methods were relatively high. In particular, enthalpies
of formation calculated with the G2(MP2) and G2 procedures exhibited s
ystematic deviations from experiment which were linearly dependent upo
n the number of C-F bonds in the molecule. Application of isodesmic re
action calculations yielded values of Delta(f)H degrees(G2(MP2)), Delt
a(f)H degrees(G2), Delta(f)H degrees(CBS-Q), and Delta(f)H degrees(CBS
-QCI/APNO) that were in remarkably close agreement with experiment. Th
is technique had no significant effect on the quality of results from
the AEQ, BAC-MP4, and CBS-4 methods.