Atomic-scale description of interfaces in rutile/sodium silicate glass-crystal composites

• Published in: Physical chemistry chemical physics : PCCP Vol. 2; no. 26; pp. 17624 - 17636
• Main Authors: Fossati, Paul C. M, Rushton, Michael J. D, Lee, William E
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 2018
• Subjects: Atomic structure; Computer simulation; Condensed Matter; Crystal structure; Crystal surfaces; Crystals; Free surfaces; Glass; Interfacial properties; Materials Science; Molecular chains; Molecular dynamics; Physics; Silicon dioxide; Sodium silicates; Titanium dioxide
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c8cp00675j

In this work interfaces between (Na 2 O) x (SiO 2 ) 1− x glasses (for x = 0.0, 0.1 and 0.2) and TiO 2 crystals are simulated using molecular dynamics and empirical potentials. Interfaces are presented for the distinct terminating surfaces of TiO 2 with Miller indices ≤2, the properties of which have been investigated using atomistic models. Simulations showed that partially ordered layers had been induced in the glass close to the interfaces, with successive oxygen-rich and cation-rich planes being noted. The first silicate layer in contact with the crystal tended to be highly-structured, with Si ions occupying well-defined positions that depend on the orientation of the crystal at the interface, and showing 2-dimensional ordering depending on glass composition. Finally, interface energies were calculated. These indicated that the interface formation may stabilise a crystal surface in comparison to maintaining a free surface. Results are presented suggesting that the structural flexibility of the glass network allows it to conform to the crystal, thereby providing charge compensation and avoiding large relaxation of the crystal structure close to the interfaces. Such interfacial properties could be crucial to improving phenomenological models of glass-crystal composite properties. Investigations of glass/crystal interfaces using atomic-scale models underlined structural changes in the glass phase as it accommodates the underlying crystal structure.