Ultrahigh-pressure disordered eight-coordinated phase of MgGeO: Analogue for super-Earth mantles.

MgGeO is important as an analog for the ultrahigh-pressure behavior of MgSiO, a major component of planetary interiors. In this study, we have investigated magnesium germanate to 275 GPa and over 2,000 K using a laser-heated diamond anvil cell combined with in situ synchrotron X-ray diffraction and density functional theory (DFT) computations. The experimental results are consistent with the formation of a phase with disordered Mg and Ge, in which germanium adopts eightfold coordination with oxygen: the cubic, ThP-type structure.

Structural response of α-quartz under plate-impact shock compression.

Because of its far-reaching applications in geophysics and materials science, quartz has been one of the most extensively examined materials under dynamic compression. Despite 50 years of active research, questions remain concerning the structure and transformation of SiO under shock compression. Continuum gas-gun studies have established that under shock loading quartz transforms through an assumed mixed-phase region to a dense high-pressure phase.

In situ X-Ray Diffraction of Shock-Compressed Fused Silica.

Because of its widespread applications in materials science and geophysics, SiO_{2} has been extensively examined under shock compression. Both quartz and fused silica transform through a so-called "mixed-phase region" to a dense, low compressibility high-pressure phase. For decades, the nature of this phase has been a subject of debate.