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A proposed modification of CBS-4M model chemistry for application to molecules of increasing molecular size

Research paper by Rois Benassi

Indexed on: 01 Sep '01Published on: 01 Sep '01Published in: Theoretical Chemistry Accounts



Abstract

 In order to calculate more accurately the enthalpies of formation, ΔHf°(298 K), for large molecules using the CBS-4M method, a new formulation of the empirical higher-level correction to the energy is proposed: ΔE=a|S|2iiIii+b(nα+nβ)+cΔ<S2>+Σnidi. The new methodology (CBS-4MB) applied to a set of 114 molecules of different size significantly decreases the mean absolute deviation from 3.78 to 2.06 kcal/mol.