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Correlation energy contributions to reaction heats
Author(s) -
George Philip,
Trachtman Mendel,
Brett Alistair M.,
Bock Charles W.
Publication year - 1977
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560120107
Subject(s) - chemistry , lone pair , open shell , valence (chemistry) , atomic orbital , electron pair , electronic correlation , molecule , valence electron , atomic physics , electron shell , molecular orbital , standard enthalpy of formation , computational chemistry , electron , physics , ion , quantum mechanics , organic chemistry , ionization
New, more accurate, Hartree‐Fock limit energies ( E HF ) for ethane and ethylene are obtained from SCF total molecular energie using Ermler and Kern's procedure. These results, together with E HF values for other small closed shell molecules, are employed to calculate correlation energy ( E c ) contributions to reaction heats. Cancellation to within 98% of the total E c involved, and often to more than 99%, is found for a wide variety of chemical reactions, which strongly suggests that there are systematic regularities in the contribution to E c from the different kinds of electron pairs in the valence shell. Assuming trictly localized pairs occupying orbitals having strongly directional character, E c for the valence shell is evaluated in terms of E c per lone pair, E c per XH bond, and E c per X/X shared pair for Ne and for molecules containing first row atoms, where X is C, N, O, and F.