Changes in the local environment surrounding magnesium ions in fragile MgO-SiO2 liquids
Changes in the local environment surrounding magnesium ions in fragile MgO-SiO2 liquids
复制标题
易碎 MgO-SiO2 液体中镁离子周围局部环境的变化
DOI：
10.1209/0295-5075/89/26005
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
J. Weber
中科院分区：
文献类型：
--
作者：
M. Wilding;C. Benmore;J. Weber
在原位收集了一系列介于顽辉石和橄榄石（MgSiO3和Mg2SiO4）之间的硅酸镁液体的x射线衍射数据。从这些数据得到的对分布函数表明，镁离子周围的局部氧环境与等效玻璃中的氧环境形成了对比。我们发现在42和38摩尔%SiO2之间有一个过渡窗口，其中镁的平均配位数在冷却时从液态的Mg-O配位数为~ 5.1±0.2变化到玻璃中的值为4.5±0.1。这种结构的变化反映了液体中稀疏聚合的硅酸盐网络和无序的镁框架之间的竞争，而硅酸盐网络在玻璃中占主导地位。
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 (MgSiO3 and Mg2SiO4). 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 %SiO2 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.