Science Highlights

CDAC Science at the 2019 SSAP Symposium

CDAC Science was on display at the recent 2019 SSAP Symposium, held in Albuquerque, NM on February 18-20.  The meeting included an overview of the year’s highlights by CDAC Director Russell Hemley along with the work of nine CDAC graduate students featured at the poster session.  Three CDAC graduate students won “Best Poster” awards for their presentations.

 

 

CDAC Scientists Provide Evidence for Near Room Temperature Superconductivity

For decades, room-temperature superconductivity has been one of physics’ ultimate goals, a Holy Grail-like objective that seems to keep drifting within realization yet always stubbornly out of reach. Various materials, theories, and techniques have been proposed and explored in search of this objective, but its realization has remained elusive. Recent experimental work on hydrogen-rich materials at high pressures is finally opening the pathway to practical superconductivity and its vast potential.

 

 

The Insulator-Metal Transition in Fluid Deuterium

The transition of elemental hydrogen from the molecular, insulating state to the monoatomic, metallic state has been a forefront problem in condensed matter physics for nearly a century, and a wide range of experimental and theoretical studies have been aimed at understanding insulator-to-metal transitions in both the solid and fluid states. Although most of the attention has been focused on the solid state…

 

 

Expanding High-Pressure Neutron Diffraction Applications

Extreme conditions research cannot be accomplished without state-of-the-art instruments. Thus, tools must be improved in order to access new domains and to expand the range of properties measured. In high pressure neutron diffraction, for example, one limitation that sample sizes need to be much larger than is the case for x-ray…

 

 


Hydrogen Melting at Extremes

The properties of hydrogen at extreme pressures and temperatures are of great interest to condensed matter physics, astrophysics, and planetary science due to the element’s putative simplicity and abundance in the visible universe. Of particular interest is the desire to know pressure-temperature conditions over which hydrogen is…

 

 

 


New High Tc Superhydrides

Extending his original predictions for metallic hydrogen, Cornell’s Neil Ashcroft later proposed that hydrogen-rich materials containing main group elements might exhibit superconductivity at accessible pressures. The hydrogen in these structures, he argued, may be considered “chemically precompressed.” These proposals, which were based on the…

 

 

 


Anharmonicity in Cementite

Cementite is the most common carbide compound in steels and has also been proposed as a host for the light element in Earth’s core. Because the material is metastable at ambient pressure and temperature, its synthesis is challenging, and high pressure techniques are required. As a result, key thermodynamic properties, particularly…

 

 

 


New High-Pressure Mineral – Hemleyite

A new paper reports the discovery and characterization of a new iron-rich high-pressure mineral named for CDAC Director Russell J. Hemley in recognition of his distinguished contributions to high-pressure research and mineral physics. The new mineral is the iron-rich analogue of akimotoite, a mineral with MgSiO3 composition and…

 

 

 


Diamonds are Forever for Science

In a recent article in The Washington Post, CDAC Director Russell Hemley weighs in on the extraordinary properties of diamond that make it so important in new scientific and technological applications. “Forget the ring: Lab-grown diamond’s are a scientist’s best friend,” published on the front page of the Post’s February 14th…

 

 

 


Superconducting Hydrogen Salt

BaReH9 is the most hydrogen-rich inorganic salt discovered thus far, and is of great interest in the study of superconductivity in dense hydrides and also the metallization of hydrogen at high pressure. The unusual composition of this material suggests that investigation of its high pressure properties should offer a number of important insights…

 

 

 


Shocking Boron Carbide

Boron Carbide exhibits a number of important material properties, among them extreme hardness approaching that of diamond, and a very high melting point. However, it is the low density of the material that makes it attractive for applications requiring high mechanical strength and light weight. Its properties are due to the unique crystal…

 

 

 


Nanocrystalline to Megabar

A recent advance toward the goal of increasing achievable static pressures beyond the mechanical limits imposed by the diamond anvil cell has been in the development of “two-stage” diamond anvils. Two-stage anvils consist of a small “micro-anvil” with a culet size on the order of 30 microns fixed onto the culet of a larger diamond anvil with a…

 

 

 


Pressure-Initiated Polymerization

Chemical reactions involving acetonitrile most often occur as the result of activating the C-N triple bond, while the C-H bonds are generally considered inert. Weak intermolecular hydrogen bonds of the N – – H – C type, however are susceptible to modification by applied pressure. Now a group including CDAC Research Scientist Zhenxian Liu, have…

 

 

 


Unexpected Topology of Dense Hydrogen

Understanding the behavior of dense hydrogen remains a major challenge in both condensed matter physics and energy science, and high-pressure experiments and theoretical calculations have uncovered a number of novel phenomena in this fundamental system. Theoretical work by CDAC Research Scientist Ivan Naumov and CDAC Director Russell J. Hemley…

 

 

 


Bonding Iron and Bismuth

It has long been recognized that applied pressure can significantly change the conventional patterns of chemical reactivity predicted by the structure of the Periodic Table. At the same time, among thousands of known interactions between elements in the Periodic Table, there remain chemical bonds that are curiously absent. But is high pressure…

 


Topological Transition in FeTi

Using computational theory as well as x-ray and neutron scattering scattering measurements, the CDAC group at Caltech has shown that the alloy FeTi undergoes an unusual change in phonon dynamics associated with changes in its electronic properties at high temperatures. This research effort included current CDAC student Fred Yang and CDAC Academic…

 

 

 


Ultrahard Carbon-BN Nanocomposite

Materials combining the hardness and strength of diamond with the higher thermal stability of cubic boron nitride (cBN) have broad potential value in science and engineering. Reacting nanodiamond with cBN at high pressures and high temperatures provides a pathway to such materials. CDAC partner Steve Jacobsen (Northwestern), along with scientists…

 

 

 


Properties of Depleted Uranium Determined

Depleted uranium and its alloys are important engineering materials due to their high density. It is well known that depleted uranium can be alloyed to improve several elastic and plastic related properties, to enhance corrosion resistance, and to allow flexible heat treatability. In recent experiments performed at HPCAT, CDAC Steering Committee…

 

 

 


Hydrogen – Through a Gas Darkly

Hydrogen is the most abundant element in the cosmos. It’s also the simplest, with only a single electron in each atom, and forms a transparent gas under ordinary conditions. But that simplicity is deceptive, for example, at the extreme pressures and temperatures found inside of giant planets. New work published in Physical Review Letters shows…

 

 

 


Intermediate Valence State in SmB6

Applied pressure is a powerful tool for studying rare earth systems with intermediate valence because their electronic states are sensitive to small changes in interatomic separation. Recent experiments at HPCAT using resonant x-ray emission spectroscopy have explored the pressure dependence of the f-electron occupancy in the Kondo insulator SmB6

 

 

 


Swapping Sodium in Battery Materials

The sodium counterpart to LiFePO4 has recently attracted attention as a potentially promising cathode material. Sodium is one of the major rock-forming elements in the Earth’s crust and is both environmentally abundant and affordable. As a result, the development of sodium analogues to lithium cathode materials is appealing, especially for large…

 

 

 


Tabletop High-Speed Impacts

A new technology platform to study high-speed impacts on a tabletop has been developed at the University of Illinois. This method uses a laser to launch thin metal foils at km/s velocities. Although “laser-launched flyer plates” have been studied for more than 30 years, they have not been broadly utilized in shock compression science partly due to…

 


Making Diamond at Atmospheric Pressure

Producing materials by chemical vapor deposition (CVD) has become an important means of synthesis, in which high-energy molecular and atomic species generate a kinetically stable phase trapped in local energy minimum. Single crystal, polycrystalline, and nanocrystalline diamond now can be produced by microwave plasma assisted CVD (MPCVD).

 

 

 


From Metal to Insulator and Back Again

New work from Carnegie scientists Russell Hemley and Ivan Naumov hones in on the physics underlying the recently discovered fact that some metals stop being metallic under pressure. Metals are compounds that are capable of conducting the flow of electrons that make up an electric current. Other materials, called insulators, are not capable of…

 

 

 


NSLS II IR Beamline Moves Forward

The Frontier Synchrotron Infrared Spectroscopy (FIS) Beamline under Extreme Conditions has been approved as one of the eight NxtGen beamlines to be developed and constructed at NSLS-II. FIS is the successor of the IR-DAC facility (U2A) at NSLS, the highly productive, Carnegie-managed user facility supported by COMPRES and CDAC, and the only…

 

 

 

 


New Light on Dense Hydrogen

New work from a team of Carnegie scientists including Chang-sheng Zha, Zhenxian Liu, Muhtar Ahart, Reinhard Boehler, and Russell Hemley using intense infrared radiation shines new light on the fundamental material hydrogen at extreme pressures and reveals the details of a surprising new form of the solid under these conditions.

 

 

 

 


Matter under Extremes

The study of matter at extreme conditions represents a forefront area of research activity across the sciences, including physics, chemistry, materials science and even biology. Advancing the frontier of extreme conditions science requires powerful micro- sampling probes to access minute samples through the vessel walls and to separate weak sample…


First Gas-gun Shock Wave Experiments at a Synchrotron

Material emissivity measurements at extreme conditions can provide fundamentally important data that allow the measurement of temperature on short time scales, which is crucial for the complete characterization of dynamic compression events. For opaque materials such as metals, reflectivity measurements are necessary and must be conducted under…

 


 

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