Molecular dynamics simulation of the effect of the Al-O-Al linkage on the P&1macr;-I&1macr; phase transition of anorthite |
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Authors: | A Miyake K Kawamura M Kitamura |
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Institution: | (1) Department of Geology and Mineralogy, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan e-mail: miyake@geo.titech.ac.jp, JP;(2) Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8551, Japan, JP |
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Abstract: | Molecular dynamics (MD) simulations of the influence of the Al-O-Al linkage on the P&1macr;-I&1macr; phase transition of
pure anorthite (An) were carried out using two different types of structures with fully ordered (FO) and partially disordered
(PD) arrangements of Al/Si in tetrahedral sites. Discontinuous changes in unit cell volumes and structure factors at the transition
temperature were observed in FO-An but not in PD-An. These results show that the orders of the transitions of FO-An and PD-An
are first and non-first, respectively. In both structures, the motions of the Ca atoms and the framework are strongly correlated
with each other during the transition and Ca atoms dominate the system. Since high-temperature X-ray studies have shown that
the transition of natural anorthite is non-first order, it is suggested that the natural anorthite has a partially disordered
arrangement of Al and Si atoms.
Received: 22 October 1998 / Revised, accepted: 12 March 1999 |
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Keywords: | Molecular dynamics simulation anorthite Al-O-Al linkage P& 1macr -I& 1macr phase transition Ca position |
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