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Molecular dynamics simulation of methanolic and ethanolic silica-based sol-gel solutions at ambient temperature and pressure

Pereira, JCG; Catlow, CRA; Price, GD; (2002) Molecular dynamics simulation of methanolic and ethanolic silica-based sol-gel solutions at ambient temperature and pressure. J PHYS CHEM A , 106 (1) 130 - 148. 10.1021/jp010078h.

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Abstract

We use molecular dynamics simulations to model realistic silica-based sol-gel solutions containing water, the simplest alcohols (MeOH and EtOH), the simplest silica alkoxides (Si(OMe)(4) and Si(OEt)(4)), and small silica clusters (Si(OH)(4), Si2O(OH)(6), and Si3O3(OH)(6)), at ambient conditions. This work builds on our previous studies simulating liquid water, methanol, ethanol, Si(OMe)(4), and Si(OEt)(4), for different conditions of pressure and temperature! Twelve solutions were simulated during 500 ps, using two different MD codes, DISCOVER and DL_POLY, with slightly different implementations and force fields, to guarantee that the results are not sensitive to details of the simulations. The same methodology is employed throughout to derive potentials for different species, liquid compositions, and thermodynamic conditions. The results obtained with both codes show that silica clusters tend to aggregate, even in dilute solutions, as observed in experimental work-a necessary step before condensation reactions can occur. According to our tests, these results are essentially independent of the initial configuration chosen for the solutions. The solvation environment around the various silica clusters (monomers, dimers and trimer rings) was also investigated, as it gives valuable insight into the diffusional and reaction mechanisms occurring in these solutions.

Type:Article
Title:Molecular dynamics simulation of methanolic and ethanolic silica-based sol-gel solutions at ambient temperature and pressure
DOI:10.1021/jp010078h
Keywords:MECHANICAL POTENTIAL SURFACES, AB-INITIO, POLYMERIZATION, KINETICS, CLUSTERS, CHEMISTRY, MODELS, GLASS, NMR, CONDENSATION
UCL classification:UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Chemistry
UCL > VP Research

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