Atomic order and cluster energetics of a 17 w.t.% Si-based glass versus the liquid phase

Antipas, G. S. E. and Temleitner, László and Karalis, K. and Pusztai, László and Xenidis, A. (2013) Atomic order and cluster energetics of a 17 w.t.% Si-based glass versus the liquid phase. JOURNAL OF PHYSICS-CONDENSED MATTER, 25 (45). p. 454206. ISSN 0953-8984

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Abstract

Aerodynamic levitation of a multi component 17 w.t.% Si glass formed by rapid quenching of the melt phase was studied by high resolution X-ray diffraction (XRD) and Reverse Monte Carlo (RMC) modeling. The main local atomic order features comprised of interactions between Si, Fe and Mg polyhedra, the stereochemistry of which was on a par with literature. Both the glass and the liquid state appeared to consist of the same fundamental Si-O, Fe-O and Mg-O clusters, with only the relative number of each varying between the two. Transition from liquid to the glass involved a 3-fold decrease in uncoordinated O (to within the first minimum of the total g(r)) and a marked increase of Fe-Si-Mg polyhedra bridging O. Octahedral Fe coordination was not suggested by the RMC data. All-electron open-shell Density Functional Theory (DFT) calculations of the most prominent clusters suggested independence between the Fe oxidation state and its polyhedra O-coordination. Of secondary thermodynamic importance were indications of network-forming Fe2+ and Fe3+ distorted trigonal and tetrahedral polyhedra. In all occasions, the Fe ferrous and ferric states involved comparable binding energies within similar clusters which indicate a dynamic equilibrium between the two.

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