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Atom equivalents for relating ab initio energies to enthalpies of formation

✍ Scribed by Mustafa R. Ibrahim; Paul Von Ragué Schleyer

Publisher
John Wiley and Sons
Year
1985
Tongue
English
Weight
887 KB
Volume
6
Category
Article
ISSN
0192-8651

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✦ Synopsis

Sets of atom equivalents have been developed which permit the estimation of heats of formation, AH0f2Yg), from ab initio total energies (3-21G and 6-31G* basis sets). This extends the isodesmic reaction scheme of Pople and the group equivalents of Wiberg. A variety of small inorganic and organic molecules, including fluorocarbons, free radicals, carbocations, and protonated species give excellent agreement with experiment; average errors are less than 1 kcal/mol with unstrained hydrocarbons (both basis sets), and are on the order of 2 kcal/mol for all molecules considered (6-31G*; the 3-21G basis errors, as expected, usually are somewhat higher). The results substantiate Pople's early conclusions that Hartree-Fock theory provides a generally satisfactory description of classical molecules.

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