http://www.cnr.it/ontology/cnr/individuo/prodotto/ID194754
Energetics and Bonding in Aluminosilicate Rings with Alkali Metal and Alkaline-Earth Metal Charge-Compensating Cations (Articolo in rivista)
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- Energetics and Bonding in Aluminosilicate Rings with Alkali Metal and Alkaline-Earth Metal Charge-Compensating Cations (Articolo in rivista) (literal)
- Anno
- 2012-01-01T00:00:00+01:00 (literal)
- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#doi
- 10.1021/jp302839f (literal)
- Alternative label
C. Gatti, G. Ottonello, P.R. Richet (2012)
Energetics and Bonding in Aluminosilicate Rings with Alkali Metal and Alkaline-Earth Metal Charge-Compensating Cations
in The journal of physical chemistry. A; ACS, American chemical society, Washington, DC (Stati Uniti d'America)
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- C. Gatti, G. Ottonello, P.R. Richet (literal)
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- ISI Web of Science (WOS) (literal)
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- 1. CNR-ISTM, c/o Dipartimento di Chimica, Universita? degli Studi di Milano, Via C. Golgi, 19-20133 Milano, Italy
2. Dipartimento di Scienze della Terra, dell'Ambiente e della Vita (DISTAV), Università di Genova, Corso Europa 26, 16132 Genova, Italy
3. Institut de Physique du Globe de Paris, 1 rue Jussieu, 75005 Paris, France (literal)
- Titolo
- Energetics and Bonding in Aluminosilicate Rings with Alkali Metal and Alkaline-Earth Metal Charge-Compensating Cations (literal)
- Abstract
- The stabilizing effect of alkali and alkaline-earth metal ions on the oxygen donors of four- and six-membered faujausite-like rings has been calculated in terms of Kohn-Sham core-level (O1s) energy shifts with respect to these same complexes without cations. The results confirm and complement earlier investigations
by Vayssilov and co-workers where Na+ and K+ were the only complexing cations. The oxygen donor centers in six-membered rings are stabilized by -3.6 ± 0.4, -3.9 ±0.5, -7.3 ± 0.1, and -7.6 ± 0.2 eV by K+, Na+, Ca2+, and Mg2+ adions, respectively. The energy shifts are even greater for four-membered rings where the stabilization effects attain -3.7 ± 0.1, -4.1 ± 0.1, -8.1 ± 0.1, and -9.0 ± 0.1 eV, respectively.
These effects are also observed on the low-lying ?-bonding and antibonding molecular orbitals (MOs) of the oxygen framework, but in a less systematic fashion. Clear relationships with the core-level shifts are found when the effects of alkali metal complexation are evaluated through electron localization/delocalization indices, which are defined in terms of the whole wave function and not just of the individual orbitals. Complexation with cations not only involves a small but significant electron sharing of the cation with the oxygen atoms in the ring but also enhances electron exchange among oxygen atoms while reducing that between the O atoms and the Si or Al atoms bonded to them. Such changes slightly increase from Na to K and from Mg to Ca, whereas they are significantly enhanced for alkaline-earth metals relative to alkali metals. With respect to Al-free complexes, Si/Al substitution and cation charge compensation generally enhance electron delocalization among the O atoms, except between those that are linked through an Al atom, and cause either an increased or a decreased Si-O ionicity (smaller/higher electron exchange) depending on the position of O in the chain relative to the Al atom(s). The generally increased electron delocalization among O atoms in the ring is induced by significant electron transfer from the adsorbed metal to the atoms in the ring. This same transfer establishes an electric field that leads to a noticeable change in the ring-atom core-level energies. The observed shifts are larger for the oxygen atoms because, being negatively charged, they are more easily polarizable than Al and Si. The enhanced electron delocalization among O atoms upon cation complexation is also manifest in Pauling's double-bond nature of the bent ?-bonding MO between nonadjacent oxygen centers in O-based ring structures. (literal)
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