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Group connectivity in binary silicate glasses: A quasi-chemical approach and molecular dynamics simulation

Journal of Non-Crystalline Solids
Publication Date
DOI: 10.1016/j.jnoncrysol.2007.06.078
  • Transport Properties – Liquids
  • Molecular Dynamics
  • Alkali Silicates
  • Phases And Equilibria
  • Nmr
  • Mas-Nmr And Nqr
  • Medium-Range Order
  • Chemistry


Abstract The medium-range order of molecular dynamics (MD) simulated binary alkali silicate glass with 5, 10, 15, 20, 25, and 33.3 mol% of Na 2O is studied in terms of the connectivity groups Q n , a 1 , … , a n , where n stands for the number of bridging oxygen atoms, and a 1, …, a n indicate the type of the connected Q n units. MD structure significantly deviates from the random connectivity model. The deviations were quantified by means of the quasi-chemical approach. The interchange energy between Q 3 and Q 4 units was found to be negative, indicating preferential formation of Q 3–Q 4 connections. This means that no tendency to phase separation was observed. Although alkali cations were apparently non-homogeneously distributed in space, regions abounding in Q 3–Q 3 and Q 4–Q 4 connections were not formed. It was suggested that grouping of alkali cations can be also mediated by the Q 4, 4433 groups.

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