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|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|
|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.|
|ISI #: ||A1993LC87000029|
|Type: ||Journal Contribution|
|Appears in Collections: ||Research publications|
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