Atomistic Calculations of Lattice Constants of Mullite with Its Compositions
Resource
Journal of the European Ceramic Society 28 (2): 345-351
Journal
Journal of the European Ceramic Society
Journal Volume
28
Journal Issue
2
Pages
345-351
Date Issued
2008
Date
2008
Author(s)
Abstract
We calculate lattice constants a and b of mullite with its compositions (Al2[Al2+2xSi2-2x]O10-x) using the constant stress molecular dynamics (MD) method. The Matsui's and Winkler's interatomic models for aluminosilicate are adapted. Two sets of mullite models are considered, one with a random distribution of oxygen vacancies and Al/Si substitutions and the other with a partially ordered Al occupancy at the T* sites. All the simulation results predict the trend observed in experiments in which the lattice constant a increases while b decreases when the x-value increases. The expansion mechanism induced by Al/Si substitutions is supported by bond length analysis. The reduction of lattice constant b is supported by the locally anisotropic atom displacement in the a and b directions sensed by the oxygen vacancies. We conclude that the causes of lattice expansion and reduction are tightly interwoven with the coexistence of vacancies and Al/Si substitutions and their inherent influence on atom displacements. © 2007 Elsevier Ltd. All rights reserved.
Type
journal article
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