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Factors affecting ionicity in all-silica materials: A density functional cluster study

Zwijnenburg, MA; Bromley, ST; van Alsenoy, C; Maschmeyer, T; (2002) Factors affecting ionicity in all-silica materials: A density functional cluster study. J PHYS CHEM A , 106 (51) 12376 - 12385. 10.1021/jp025696s.

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Abstract

Atomic charge analysis is performed on the basis of electron densities obtained from systematic density functional (DF) cluster calculations on structural fragments from seven different all-siliceous zeolites and two all-silica minerals. Charges and ionicities for these fragments are calculated Using three different charge analysis schemes: Mulliken, Hirshfeld, and Bader methods. The dependency of the ionicty of the Si-O bond on geometric parameters of the clusters is investigated and it is demonstrated that a correlation exists between the Si-O bond length and its ionicty. Ionicities derived from Bader atomic charges were shown to have a trend opposite to that of ionicities derived from Mulliken and Hirshfeld charges. A simple model is proposed to account for these differences, demonstrating that these opposing trends may he reconciled. The results also suggest a possible link between Si-O bond ionicity and the energetic stability of the corresponding bulk silica polymorph.

Type:Article
Title:Factors affecting ionicity in all-silica materials: A density functional cluster study
DOI:10.1021/jp025696s
Keywords:MOLECULAR-ORBITAL THEORY, EXTENDED BASIS-SETS, VALENCE BASIS-SETS, AB-INITIO, ORGANOMETALLIC COMPOUNDS, QUANTITATIVE-DETERMINATION, TRANSITION-METALS, LATTICE-DYNAMICS, ALPHA-QUARTZ, ZEOLITES
UCL classification:UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Chemistry

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