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Atom equivalents for relating ab initio energies to enthalpies of formation
Author(s) -
Ibrahim Mustafa R.,
Von Ragué Schleyer Paul
Publication year - 1985
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.540060302
Subject(s) - isodesmic reaction , chemistry , ab initio , standard enthalpy of formation , protonation , computational chemistry , molecule , atom (system on chip) , carbocation , thermodynamics , organic chemistry , physics , ion , computer science , embedded system
Sets of atom equivalents have been developed which permit the estimation of heats of formation, ΔH° f 298 ( g ), 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.