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Please use this identifier to cite or link to this item: http://hdl.handle.net/1942/3779

Title: THE PROTONATION OF N2O REEXAMINED - A CASE-STUDY ON THE RELIABILITY OF VARIOUS ELECTRON CORRELATION METHODS FOR MINIMA AND TRANSITION-STATES
Authors: MARTIN, Jan
LEE, TJ
Issue Date: 1993
Publisher: AMER INST PHYSICS
Citation: JOURNAL OF CHEMICAL PHYSICS, 98(10). p. 7951-7957
Abstract: The protonation of N2O and the intramolecular proton transfer in N2OH+ have been studied using large basis sets in conjunction with second-order many-body perturbation theory (MP2), singles and doubles coupled cluster (CCSD), the augmented coupled cluster method [CCSD(T)], and complete active space self-consistent field (CASSCF) methods. It is shown that MP2 is inadequate even for HNNO+, which has a minor nondynamical correlation effect; for the transition state only CCSD(T) produces a reliable geometry due to serious nondynamical correlation effects. Harmonic frequencies accurate to 50 cm-1 or better are predicted for both protonated species. The proton affinity at 298.15 K is found to be 137.6 kcal/mol, in excellent agreement with the recent experimental redetermination of 137.3 +/- 1 kcal/mol; the HNNO+ isomer is found to be 4.4 kcal/mol above the HONN+ isomer, with an interconversion barrier of approximately 89 kcal/mol, herewith confirming recent experimental evidence that both species occur together with an energy difference of 6 +/- 1. 5 kcal/mol. Comparison of the traditional double-zeta plus polarization (DZP) basis and the newer correlation consistent polarized valence double zeta (cc-pVDZ) basis set appears to indicate that the latter might lead to more accurate geometries and harmonic frequencies, although a more detailed investigation would be needed before any definitive conclusions.
Notes: LIMBURGS UNIV CENTRUM,DEPT SBM,B-3590 DIEPENBEEK,BELGIUM. UNIV INSTELLING ANTWERP,DEPT CHEM,B-2610 WILRIJK,BELGIUM.
URI: http://hdl.handle.net/1942/3779
ISI #: A1993LC87000029
ISSN: 0021-9606
Type: Journal Contribution
Appears in Collections: Research publications

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