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Atomic ordering around the oxygen vacancies in sillimanite

✍ Scribed by S. Padlewski; V. Heine; G. D. Price

Publisher: Springer-Verlag
Year: 1992
Tongue: English
Weight: 622 KB
Volume: 18
Category: Article
ISSN: 0342-1791
DOI: 10.1007/bf00199418

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✦ Synopsis

Computer simulation is used to investigate the short range ordering around an isolated oxygen vacancy in sillimanite. The static lattice energy with the use of empirical potentials is calculated, for different A1/Si distributions around a vacancy in a supercell of sillimanite. A parametrisation of the total energy is built up and used to deduce the best A1/Si ordering around the oxygen vacancy. It is found that a strong ordering about the vacancy occurs. In the ab-plane two sets of aluminium cluster are found besides the vacancy, surrounded above and below by silicon atoms, a configuration that promotes local charge balance. By placing two vacancies on sites directly adjacent to the same oxygen, the central oxygen site is bonded to four cations: this situation is found to be energetically unfavourable.

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