Nonadditive effects in ternary H₂-cation-PAH systems

• Published in: Journal of computational chemistry Vol. 29; no. 11; pp. 1733 - 1739
• Main Author: Donchev, Alexander G
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.08.2008
• Subjects: ab initio study; interaction energy components; intermolecular interactions; molecular hydrogen; nonadditive effects; polyaromatic hydrocarbons
• ISSN: 0192-8651; 1096-987X
• DOI: 10.1002/jcc.20927

This article reports state-of-the-art ab initio calculations at the second order of Møller-Plesset perturbation theory of molecular hydrogen binding in its ternary complexes with lightweight alkali cations (M = Li or Na) and polycyclic aromatic hydrocarbons (PAHs) up to coronene. The study revealed a substantial nonadditive contribution to the H₂ stabilization energy. In the most stable conformation, the nonadditive contribution weakens the H₂ binding by a factor of nearly 1.5 and 1.3 for Li and Na cations, respectively, as compared with the pairwise sum of direct H₂-M⁺ and H₂-PAH contributions. In the Li case, the presence of PAH not only does not promote H₂ binding but has a large (~20%) weakening effect in comparison with the initial H₂-Li⁺ interaction. In the Na case, the presence of PAH has the usual stabilizing influence on the hydrogen binding. A careful analysis of the physical components of the nonadditive effect on the example of H₂-M⁺-benzene complexes revealed the dominating role of the induction nonadditivity.