Mechanical Properties And Electronic Structure Of Mullite Phases Using First-Principles Modeling

In this feature article, Aryal, Rulis and Ching from the University of Missouri-Kansas City describe a systematic and detailed theoretical investigation of the structures and properties of the phases in the aluminosilicate series Al4+2xSi2-2xO10-x, where x is 0 to 1. They constructed many stoichiometric supercell models for the four well-known mullite phases in the series (3Al2O3∙3SiO2, 2Al2O3∙SiO2, 4Al2O3∙SiO2 and 9Al2O3∙SiO2) using experimentally reported crystal structures and systematic removal of selected atoms at the partially occupied sites to maintain charge neutrality. Aryal, Rulis and Ching then studied the electronic structure and mechanical properties of the series (as well as sillimanite, where x = 0, and silica-free τ-Al2O3, where x = 1) using first-principles calculations. They suggest that the first-principles results explain the experimentally observed structure and properties of mullite phases and their trends with x at the fundamental level.