Theoretical characterization of dihydrogen adducts with halide anions
- Dipartimento di Chimica IFM and NIS Centre of Excellence, Universita di Torino, INSTM UdR Universita, Via Pietro Giuria 7, 10125 Turin (Italy)
The interaction between a hydrogen molecule and the halide anions F{sup -}, Cl{sup -}, Br{sup -}, and I{sup -} has been studied at different levels of theory and with different basis sets. The most stable configurations of the complexes have a linear geometry, while the t-shaped complexes are saddle points on the potential energy surface, opposite to what is observed for alkali cations. An electrostatic analysis conducted on the resulting adducts has highlighted the predominance of the electrostatic term in the complexation energy and, in particular, of the quadrupole- and dipole-polarizability dependent contributions. Another striking difference with respect to the positive ions, is the fact that although the binding energies have similar values (ranging between 25 and 3 kJ/mol for F{sup -} and I{sup -}, respectively), the vibrational shift of the {nu}-tilde{sub H-H} and in general the perturbation of the hydrogen molecule in complexes are much greater in the complexes with anions ({delta}{nu}-tilde{sub H-H} ranges between -720 and -65 cm{sup -1}). Another difference with respect to the interaction with cations is a larger charge transfer from the anion to the hydrogen molecule. The {delta}{nu}-tilde is the result of the cooperative role of the electrostatics and of the charge transfer in the interaction. The correlation between binding energies and vibrational shift is far from linear, contrary to what is observed for cation complexes, in accordance with the higher polarizability and dynamic polarizability of the molecule along the molecular axis. The observed correlation may be valuable in the interpretation of spectra and thermodynamic properties of adsorbed H{sub 2} in storage materials.
- OSTI ID:
- 20783301
- Journal Information:
- Journal of Chemical Physics, Vol. 124, Issue 22; Other Information: DOI: 10.1063/1.2202730; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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