Institut für Geologie und Mineralogie, Universität zu Köln, 50674 Köln, Germany;
Center for Advanced Radiation Sources, University of Chicago, Chicago, IL 60637.
Proc Natl Acad Sci U S A. 2017 Sep 19;114(38):10041-10046. doi: 10.1073/pnas.1708882114. Epub 2017 Sep 5.
We investigated the structure of SiO glass up to 172 GPa using high-energy X-ray diffraction. The combination of a multichannel collimator with diamond anvil cells enabled the measurement of structural changes in silica glass with total X-ray diffraction to previously unachievable pressures. We show that SiO first undergoes a change in Si-O coordination number from fourfold to sixfold between 15 and 50 GPa, in agreement with previous investigations. Above 50 GPa, the estimated coordination number continuously increases from 6 to 6.8 at 172 GPa. Si-O bond length shows first an increase due to the fourfold to sixfold coordination change and then a smaller linear decrease up to 172 GPa. We reconcile the changes in relation to the oxygen-packing fraction, showing that oxygen packing decreases at ultrahigh pressures to accommodate the higher than sixfold Si-O coordination. These results give experimental insight into the structural changes of silicate glasses as analogue materials for silicate melts at ultrahigh pressures.
我们使用高能 X 射线衍射研究了高达 172GPa 的 SiO 玻璃的结构。多通道准直器与金刚石压腔的结合使得以前无法达到的压力下对二氧化硅玻璃的结构变化进行全 X 射线衍射测量成为可能。我们表明，SiO 在 15 到 50GPa 之间首先经历了 Si-O 配位数从四配位到六配位的变化，这与先前的研究结果一致。在 50GPa 以上，估计的配位数在 172GPa 时连续从 6 增加到 6.8。Si-O 键长首先由于四配位到六配位的变化而增加，然后在 172GPa 之前以较小的线性减少。我们将这些变化与氧堆积分数联系起来，表明在超高压下氧的堆积减少，以适应高于六配位的 Si-O 配位。这些结果为高压下硅酸盐熔体类似物的硅酸盐玻璃结构变化提供了实验上的深入了解。
