The structure and energetics of the HCN → HNC transition state

Timothy J. Lee, Alistair P. Rendell

Research output: Contribution to journalArticle

101 Citations (Scopus)

Abstract

The optimum geometries and quadratic force constants of HCN, HNC and the transition state connecting them have been determined at the single and double excitation coupled-cluster (CCSD) and CCSD(T) levels of theory. Energy differences were evaluated using the CCSD and CCSD(T) methods in conjunction with large atomic natural orbital basis sets containing g-type basis functions on the heavy atoms and f-type functions on hydrogen. The most reliable structure obtained for the transition state has bond distances of 1.194, 1.188 and 1.389 Å for rCN, rCH and rNH, respectively. Including a correction for zero-point vibrational energies, the transition state is predicted to be 44.6 ± 1.0 kcal/mol above the HCN isomer, while HNC is predicted to be 14.4 ± 1.0 kcal/mol above HCN. The latter value is in excellent agreement with the most recent experimental determination (14.8 ± 2.0 kcal/mol).

Original languageEnglish
Pages (from-to)491-497
Number of pages7
JournalChemical Physics Letters
Volume177
Issue number6
DOIs
Publication statusPublished - 8 Mar 1991
Externally publishedYes

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