In-Situ X-ray Diffraction Study of Silicate Melt Structure at High Pressures and Temperatures

我们研究高压下液体结构的新技术使我们有可能测量（1）相对低温的元素液体（如液态Te、液态Si和液态Ge）（最高达20GPa）和（2）硅酸盐熔体（如MgSiO_3熔体和CaSiO_3熔体）（最高达6GPa）中的结构变化。我们的论文详细报道了（2）的结果，这可能是该研究领域第一篇在国际期刊上发表的论文，论文的摘要是“我们发展了研究硅酸盐熔体结构的同步辐射X射线衍射技术，并将其应用于测量MgSiO_3和CaSiO_3熔体的结构，测量压力高达6GPa。在这两种熔体中，二价离子周围的局域结构和SiO_4四面体的网络结构的变化是主要的压缩机制，而Si离子周围的局域结构的变化是次要的压缩机制。CaSiO_3熔体中的结构变化比MgSiO_3熔体中的大，特别是在常压附近。这些结果与MgSiO_3和CaSiO_3的实验和理论信息一致，并解释了以前工作中的差异。我们在高压下硅酸盐熔体结构的测量方面取得了一些进展。但正如论文标题所示，该研究仍处于“探索性”阶段，需要进一步发展实验技术，例如，扩大压力极限。

Our new techniques for studying the structure of liquids at high pressures make it possible to measure the structural changes in (1) elemental liquids with relatively low temperatures, such as liquid Te, liquid Si, and liquid Ge, up to above 20 GPa and (2) silicate melts, such as MgSiO_3 melt and CaSiO_3 melt, up to 6 GPa. Our paper that reports results of (2) in detail may be the first paper of this research field published in an international journal.The abstract of the paper is "We have developed synchrotron X-ray diffraction techniques for studying the structure of silicate melts and have applied them to measuring the structures of MgSiO_3 and CaSiO_3 melts up to 6 GPa. In both melts, it appears that the changes in the local structure around the divalent ions and in the network structure of SiO_4 tetrahedra are the dominant compression mechanisms while a change in the local structure around the Si ion is a secondary mechanism up to at least 6 GPa. The structural changes appear to be larger in CaSiO_3 melt than in MgSiO_3 melt, especially in the vicinity of ambient pressure. These results are consistent with available experimental and theoretical information on MgSiO_3 and CaSiO_3, and explain discrepancies in previous work". We attain some progress in measurements of silicate melt structure at high pressures. However, as shown in the title of the paper, the research is still "exploratory" and requires further development of experimental techniques, for example, to extend the pressure limit.