Recent HP-XSD Science Highlights

Recent discoveries of several stable dense hydrous minerals at high pressure–temperature conditions have led to an important implication of a massive water reservoir in the Earth’s lower mantle. A research team used HPCAT facility and demonstrated that (Fe,Al)OOH can be stabilized in a hexagonal lattice at 107–136 GPa and 2,400 K. By combining powder X-ray-diffraction techniques with multigrain indexation, the team has determined this hexagonal hydrous phase with a = 10.5803(6) Å and c = 2.5897(3) Å at 110 GPa, which is stable under the deep lower mantle conditions and can transform to the… more

Topological Kondo insulator possesses characteristics of both the strong electron correlations and the topological configurations, as shown in a mixed-valence material SmB6. YbB6 is a structural analog of SmB6, but remains controversial whether compressed YbB6 material is a topological insulator or a Kondo topological insulator. A research team used HPCAT facility and performed x-ray measurements on YbB6samples. Both the high-pressure powder x-ray diffraction and optical Raman measurements show no trace of structural phase transitions… more

By engineering molecules with mechanically heterogeneous components with a compressible (‘soft’) mechanophore and incompressible (‘hard’) ligands, a research team has created ‘molecular anvils’, resulting in isotropic stress that leads to relative motions of the rigid ligands, anisotropically deforming the compressible mechanophore and activating bonds. Conversely, rigid ligands in steric contact impede relative motion, blocking reactivity. X-ray experiments, including the use of x-ray absorption measurements at HPCAT, demonstrate hydrostatic-pressure-driven redox reactions in metal–… more

At temperatures (<319 K or <46 oC) where life is sustained, water is an abnormal liquid, having a number of anomalous properties. For instance, water displays minima of isobaric heat capacity at 308 K and isothermal compressibility at 319 K which are related to entropy and density fluctuations, respectively. It has been widely accepted that water’s anomalies are not a result of simple thermal fluctuation, but are connected to the formation of various structural aggregates in the hydrogen bonding network. To understand water’s anomalous behavior, a two-liquid model with a… more

Knowledge on the structure and properties of silicate magma under extreme pressure plays an important role in understanding the nature and evolution of Earth’s deep interior.  However, such information is scarce owing to experimental challenges.  Using a recently developed double-stage Paris-Edinburgh press, combined with the multi-angle energy dispersive X-ray diffraction, a team has measured structures of MgSiO3 glass up to 111 GPa. The results revealed direct experimental evidence of a structural change in this glass at >88 GPa. The structure above 88 GPa is interpreted as having the… more

Understanding the behavior of solids under shock compression, including transformations, their pathways, and kinetics, lies at the core of contemporary static and dynamic compression science. A team led by scientists from Sandia National Laboratories is leveraging the capabilities of two sectors of the APS, HPCAT and DCS, for real-time observations of the kinetics of a shock-driven phase transition in a simple ionic solid, CaF2, a model structure in high-pressure physics.

Traditionally, shock compression research infers phase transitions from continuum-level measurements and uses… more

Single crystal diamond is the hardest known material and widely used in studies on materials under extreme conditions. Nanocrystalline diamond (NCD) possesses hardness comparable to that of single crystal diamond, while also demonstrating increased fracture toughness and yield strength. Thus, NCD’s is a candidate material as second stage anvils to extend the maximum pressure in static high pressure technology. A research team, using Microwave Plasma Chemical Vapor Deposition, has successfully grown NCD on single crystal diamond anvil surface (Figure). The team used HPCAT facility and is… more

Nanotwinning is known as a highly effective approach for strengthening structural materials and impeding the degradation of mechanical properties. Recently a major breakthrough was realized when nanotwinned cubic-BN (nt-c-BN) and diamond (nt-diamond) were successfully synthesized from onion-like nanoparticle precursors under high pressure conditions. Understanding the microscopic origin of the twin boundaries, and the formation of such from onion-like precursors, are therefore critically important and can provide guidance to the production of nt-diamond at a larger scale. A research team… more