The electronic structure and stabilities of the symmetric gas phase anion clusters of hydrogen fluoride

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Ab initio UHF, MP2 and MP4 calculations were used to study the geometries, the electronic structure and the thermochemical stabilities of the gas phase anionic clusters of hydrogen fluoride, (HF)(n)/-, for n = 2-6. Basis sets up to the aug-cc-pVDZ set were employed. These were augmented with a 6-term even tempered (sp) cavity set. The thermochemical stabilities of these complexes against vertical ionization as well as dissociation to various products were determined. These clusters involve a single shell of two to six HF molecules complexed in a symmetrical head-to-head orientation. They show higher thermochemical stabilities than similar clusters of water and ammonia and have stabilities similar to those of the neutral hydrogen bonded clusters of hydrogen fluoride. As with water, the smallest stable anionic cluster of hydrogen fluoride has two monomers which is considerably smaller than those observed for ammonia. The integrated electron densities as well as the natural bond orbital analysis reveals that a significant portion of the excess electron density is localized in the cavity region interior to the hydrogen atoms of the inner shell. The stability of the clusters increased with the number of monomers. Cavity orbitals had a nominal effect on the properties of the complexes and effected the prediction of the geometrical features of the complexes more than their stability. © 2000 Elsevier Science B.V.

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Journal of Molecular Structure: THEOCHEM