Scientists have looked for different ways to force hydrogen into a metallic state for decades. A metallic state of hydrogen is a holy grail for materials science because it could be used for superconductors, materials that have no resistance to the flow of electrons, which increases electricity transfer efficiency many times over. For the first time researchers, led by Carnegie's Viktor Struzhkin, have experimentally produced a new class of materials blending hydrogen with sodium that could alter the superconductivity landscape and could be used for hydrogen-fuel cell storage. The research is published in Nature Communications.
It had been predicted that certain hydrogen-rich compounds consisting of multiple atoms of hydrogen with so-called alkali metals like lithium, potassium or sodium, could provide a new chemical means to alter the compound's electronic structure. This, in turn, may lead the way to metallic high-temperature superconductors.
At center, in green, is the new three-atom hydrogen 'chain.' It is surrounded by several 'normal' two-atom molecules of hydrogen, also in green. The new chain configuration appears in the new material NaH7, which was produced under high pressure and high temperature conditions. The new material could change the superconductivity landscape and be useful for hydrogen storage in hydrogen fuel cells.
Image courtesy Duck Young Kim
"The challenge is temperature," explained Struzhkin. "The only superconductors that have been produced can only exist at impractically cold temperatures. In recent years, there have been predictions of compounds with several atoms of hydrogen coupled with alkali metals that could exist at more practical temperatures. They are theorized to have unique properties useful to superconductivity."
Now, the predictions have been confirmed. The Struzhkin team included Carnegie researchers Duck Young Kim, Elissaios Stavrou, Takaki Muramatsu, Ho-Kwang Mao, and Alexander Goncharov, with researchers from other institutions.*
The team used theory to guide their experiments and measured the samples using both a method that reveals the atomic structure (X-ray diffraction) and a method that identifies molecules by characteristics such as their minute vibrations and rotations (Raman spectroscopy). Theoretically, the sodium/hydrogen material would be stable under pressure, have metallic characteristics and unique structures, and show superconducting properties.
The team conducted high-pressure/high-temperature experiments. Matter under these extreme conditions can morph into new structures with new properties. They squeezed lithium and sodium samples in a diamond anvil cell to enormous pressures while heating the samples using a laser. At pressures between 300,000 and 400,000 atmospheres (30-40 gigapascals, or GPa) and temperatures of about 3100°F (2000 kelvin), they observed, for the first time, structures of "polyhydrides," sodium with 3 hydrogen atoms (NaH3) and NaH7--sodium with seven atoms of hydrogen--in very unusual configurations. Three negative charged hydrogen atoms in the NaH7 material lined up and looked like one-dimensional hydrogen chains, which is a new phase that is very different from pure hydrogen.
"This configuration was originally predicted to exist in 1972, more than 40 years ago," remarked Duck Young Kim. "It turns out that our experiments are in complete agreement with the theory, which predicted the existence of NaH3. The bonus is that we also observed the compound with seven hydrogen atoms."
Struzhkin reflected, "Further work needs to be done to see if materials in this class can be produced at lower temperatures and pressures. But this new class of matter opens up a whole new world of possibilities."
Caption: At center, in green, is the new three-atom hydrogen "chain." It is surrounded by several "normal" two-atom molecules of hydrogen, also in green. The new chain configuration appears in the new material NaH7, which was produced under high pressure and high temperature conditions. The new material could change the superconductivity landscape and be useful for hydrogen storage in hydrogen fuel cells. Image courtesy Duck Young Kim
*Other researcher include Chris Pickard with the University College, London; Richard Needs of the Cavendish Laboratory in the UK; and Vitali Prakapenda of the University of Chicago. This work was supported by the DOE/BES; the Energy Frontier Research in Extreme Environments Center (EFree); the Engineering and Physical Sciences Research Council (EPSRC) of the UK; DARPA; and NSFC.
The Carnegie Institution for Science is a private, nonprofit organization headquartered in Washington, D.C., with six research departments throughout the U.S. Since its founding in 1902, the Carnegie Institution has been a pioneering force in basic scientific research. Carnegie scientists are leaders in plant biology, developmental biology, astronomy, materials science, global ecology, and Earth and planetary science.
Viktor Struzhkin | EurekAlert!
A new tool for discovering nanoporous materials
23.05.2017 | Ecole Polytechnique Fédérale de Lausanne
Did you know that packaging is becoming intelligent through flash systems?
23.05.2017 | Heraeus Noblelight GmbH
An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.
We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...
Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.
Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...
An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...
In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.
In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...
Dental plaque and the viscous brown slime in drainpipes are two familiar examples of bacterial biofilms. Removing such bacterial depositions from surfaces is...
23.05.2017 | Event News
22.05.2017 | Event News
17.05.2017 | Event News
23.05.2017 | Physics and Astronomy
23.05.2017 | Life Sciences
23.05.2017 | Medical Engineering