Title

Structure, Energetics and Vibrational Spectra of Dimers, Trimers, and Tetramers of HX (X = Cl, Br, I)

Document Type

Article

Journal/Book Title

Chemical Physics

Publication Date

3-1997

Publisher

Elsevier

Volume

216

Issue

1-2

First Page

37

Last Page

52

DOI

10.1016/S0301-0104(97)00012-8

Abstract

The title complexes are studied by correlated ab initio methods using a pseudopotential double-ζ basis set, augmented by diffuse sp and two sets of polarization functions. The binding energies of the complexes decrease in the order HCl > HBr > HI. In the mixed HX…HX' dimers, the nature of the proton-donor molecule is more important than is the proton-acceptor with respect to the strength of the interaction. Only one minimum is found on the potential energy surface of the trimers and tetramers, which corresponds to the Cnh cyclic structure. Enlargement of the complex leads to progressively greater individual H-bond energy and HX bond stretch, coupled with reduced intermolecular separation and smaller nonlinearity of each H-bond. Electron correlation makes a larger contribution as the atomic number of X increases. The highest degree of cooperativity is noted for oligomers of HCl and HBr, as compared to HI. The nonadditivity is dominated by terms present at the SCF level. The vibrational frequencies exhibit trends that generally parallel the energetics and geometry patterns, particularly the red shifts of the HX stretches and the intermolecular modes.

Comments

http://www.sciencedirect.com/science/article/pii/S0301010497000128

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Published by Elsevier in Chemical Physics.

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