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Reactivity of haloethanes with hydroxyl radicals: Effects of basis set and correlation energy on reaction energetics
Author(s) -
Sekušak Sanja,
Sabljic´ Aleksandar
Publication year - 1997
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/(sici)1096-987x(19970715)18:9<1190::aid-jcc7>3.0.co;2-m
Subject(s) - counterpoise , basis set , chemistry , ab initio , computational chemistry , electronic correlation , basis (linear algebra) , thermodynamics , atomic physics , density functional theory , physics , mathematics , molecule , organic chemistry , geometry
Ab initio calculations on fluoroethane reactions with thehydroxyl radical have been carried out at different levels of theory. Theconvergence of reaction barriers and reaction enthalpies has beensystematically investigated with respect to the size and quality of thebasis set and the treatment of correlation energy. The G2 and MP2 barrierheights and reaction enthalpies show the best agreement with theexperimental data. The split valence basis sets of triple‐zeta qualitysupplemented by diffuse and polarization functions are necessary toreproduce experimental values for barrier heights and reaction enthalpiesat the MP2 level of theory. The full counterpoise correction was used tocalculate the basis set superposition error for several standard basissets, including polarization and diffuse functions. The smallestcounterpoise corrections are associated with basis sets that containpolarization and diffuse functions, the diffuse functions being the mosteffective in reducing BSSE. However, in our case, the uncorrected barrierheights are in better agreement with experimental results than thecounterpoise‐corrected data. Thus, at the MP2 level of theory, which seemsto be dictated for larger electronic systems of chemical interest, theoptimal approach is to increase the basis set to the maximum sizeaffordable and to use results without counterpoise corrections for thecalculation of reaction barriers. A viable alternative is the use of G2theory because its results for the barrier heights and reaction enthalpiesare in excellent agreement with the experimental data. © 1997 John Wiley& Sons, Inc. J Comput Chem 18: 1190–1199