Characterizing modulated structures with first-principles calculations: a unified superspace scheme of ordering in mullite.

Autor: Klar PB; Departamento de Física de la Materia Condensada, Facultad de Ciencia y Tecnología, Universidad del País Vasco UPV/EHU, Apartado 644, Bilbao, 48080, Spain., Etxebarria I; Departamento de Física Aplicada II, Facultad de Ciencia y Tecnología, Universidad del País Vasco UPV/EHU, Apartado 644, Bilbao, 48080, Spain., Madariaga G; Departamento de Física de la Materia Condensada, Facultad de Ciencia y Tecnología, Universidad del País Vasco UPV/EHU, Apartado 644, Bilbao, 48080, Spain.
Jazyk: angličtina
Zdroj: Acta crystallographica. Section A, Foundations and advances [Acta Crystallogr A Found Adv] 2019 Mar 01; Vol. 75 (Pt 2), pp. 260-272. Date of Electronic Publication: 2019 Feb 12.
DOI: 10.1107/S2053273319000846
Abstrakt: The benefit of computational methods applying density functional theory for the description and understanding of modulated crystal structures is investigated. A method is presented which allows one to establish, improve and test superspace models including displacive and occupational modulation functions from first-principles calculations on commensurate structures. The total energies of different configurations allow one to distinguish stable and less stable structure models. The study is based on a series of geometrically optimized superstructures of mullite (Al 4+2x Si 2-2x O 10-x ) derived from the superspace group Pbam(α0½)0ss. Despite the disordered and structurally complex nature of mullite, the calculations on ordered superstructures are very useful for determining the ideal Al/Si ordering in mullite, extracting atomic modulation functions as well as understanding the SiO 2 -Al 2 O 3 phase diagram. The results are compared with experimentally established models which confirm the validity and utility of the presented method.
(open access.)
Databáze: MEDLINE
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