Changes in the local environment surrounding magnesium ions in fragile MgO-SiO<sub>2</sub> liquids
Wilding, M. C.; Benmore, C. J.; Weber, J. K. R.; Wilding, M. C.; Institute of Mathematical and Physical Sciences, Aberystwyth University - Aberystwyth, Ceredigion, SY23 3BZ, UK, EU; Benmore, C. J.; X-ray Science Division, Advanced Photon Source, Argonne National Laboratory 9700 Cass Avenue, Argonne, IL 60439, USA; Weber, J. K. R.; X-ray Science Division, Advanced Photon Source, Argonne National Laboratory 9700 Cass Avenue, Argonne, IL 60439, USA; Materials Development Inc. - Arlington Heights, IL 60004, USA
Журнал:
EPL (Europhysics Letters)
Дата:
2010-01-01
Аннотация:
X-ray diffraction data have been collected in situ for a series of magnesium silicate liquids between and including the two mineral compositions enstatite and forsterite (MgSiO<sub>3</sub> and Mg<sub>2</sub>SiO<sub>4</sub>). The pair distribution functions obtained from these data show that the local oxygen environment around the magnesium ions contrasts with that found in the equivalent glasses. We identify a transition window between 42 and 38 mole %SiO<sub>2</sub> where the average magnesium coordination number changes on cooling from a Mg-O coordination number of ∼5.1±0.2 in the liquid state to a value of 4.5±0.1 in the glass. This change in structure reflects a competition between a sparsely polymerised silicate network and a disordered magnesium framework in the liquid, while the silicate network dominates in the glass.
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