Atomistic calculations of lattice constants of mullite with its compositions

✍ Scribed by Jen-Chang Chen; Chuin-Shan Chen; Hartmut Schneider; Chia-Ching Chou; Wen-Cheng J. Wei

• Book ID: 104022714
• Publisher: Elsevier Science
• Year: 2008
• Tongue: English
• Weight: 494 KB
• Volume: 28
• Category: Article
• ISSN: 0955-2219
• DOI: 10.1016/j.jeurceramsoc.2007.03.001

✦ Synopsis

We calculate lattice constants a and b of mullite with its compositions (Al 2 [Al 2+2x Si 2-2x ]O 10-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.