The structure of MgO–SiO2 glasses at elevated pressure
The structure of MgO–SiO2 glasses at elevated pressure
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高压下 MgO-SiO2 玻璃的结构
DOI：
10.1088/0953-8984/24/22/225403
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
M. Tucker
中科院分区：
文献类型：
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作者：
M. Wilding;M. Guthrie;S. Kohara;C. Bull;J. Akola;M. Tucker
硅酸镁体系是一种重要的地球物理模拟物，在该体系中形成的玻璃的中子衍射数据也可以为理解相关液体的结构依赖性质提供一个初步框架，这在行星形成过程中是重要的。原位采集的单组分（38 mol% SiO2）硅酸镁玻璃样品的中子衍射数据表明，当压力从环境条件增加到环境温度下的8.6 GPa时，结构发生了局部变化。已经开发了一种获得完全校正的总结构因子S(Q)的方法，该方法可以在压缩弱散射玻璃样品时进行准确的结构表征。测得的S(Q)数据表明化学有序度随压力的变化，实空间变换显示Mg-O配位数的增加和镁离子周围局部环境的畸变。我们使用反向蒙特卡罗方法来比较高压和环境压力结构，并将高压形式与硅含量较低的玻璃（Mg2SiO4）进行比较，后者代表了更致密、无空隙和拓扑有序的结构。Mg-O配位数随着压力的增加而增加，我们还发现Si-O键的连续连接程度通过间隙的坍塌而增加。
The magnesium silicate system is an important geophysical analogue and neutron diffraction data from glasses formed in this system may also provide an initial framework for understanding the structure-dependent properties of related liquids that are important during planetary formation. Neutron diffraction data collected in situ for a single composition (38 mol% SiO2) magnesium silicate glass sample shows local changes in structure as pressure is increased from ambient conditions to 8.6 GPa at ambient temperature. A method for obtaining the fully corrected, total structure factor, S(Q), has been developed that allows accurate structural characterization as this weakly scattering glass sample is compressed. The measured S(Q) data indicate changes in chemical ordering with pressure and the real-space transforms show an increase in Mg–O coordination number and a distortion of the local environment around magnesium ions. We have used reverse Monte Carlo methods to compare the high pressure and ambient pressure structures and also compare the high pressure form with a more silica-poor glass (Mg2SiO4) that represents the approach to a more dense, void-free and topologically ordered structure. The Mg–O coordination number increases with pressure and we also find that the degree of continuous connectivity of Si–O bonds increases via a collapse of interstices.