Under extremely high pressures, pure vanadium crystals change their shape but do not take up less space as a result, unlike most other elements that undergo phase transitions. The work appears in the February 23 issue of Physical Review Letters.
Led by High Pressure Collaborative Access Team (HPCAT) research scientist Yang Ding, the team* used a diamond anvil cell to subject vanadium crystals to pressures more than 600 thousand times higher than the atmospheric pressure at sea level (which is about one bar). Using the high-resolution HPCAT x-ray facility, the scientists were able to detect that the basic atomic packing units of vanadium crystals had changed from a cube to a rhombohedron, which resembles a cube whose sides have been squashed from squares into diamond shapes.
“Trying to understand why high-pressure vanadium uniquely has the record-high superconducting temperature of all known elements inspired us to study high-pressure structure of vanadium," Ding said. “We had no idea that we would discover a completely new type of phase transition."
The most familiar phase transitions are those between gas, liquid, and solid forms. In general, increasing pressure and decreasing temperature will cause a substance to take up less space and eventually form a solid. But as a result of their atoms packing in closer together at extremely high pressures, some solids undergo further changes in their physical properties and can even change shape, which usually results in a change in volume. But in this respect, vanadium is unique.
Though it is expensive to mine and refine, vanadium is extremely important in the industrial world, where its main use is as a steel additive. Steel that contains vanadium is exceptionally strong and resistant to metal fatigue, making it ideal for kitchen knives that stay sharp almost indefinitely, and jet turbine blades that can withstand high speed and abrasion.
Pure vanadium crystals in cubic form were thought to be able to resist pressures over several million bars. Recent theoretical calculations, however, suggested that pressure could cause unusual electronic interactions in vanadium that would destroy the cubic crystals. Instead, vanadium avoids this collapse by changing to a rhombohedron.
“Although this type of transition was first observed in vanadium, it suggests that we should reexamine many other elements we thought were very stable," Ding explained. “Moreover, the transition provides a new explanation for the continuous rising of superconducting temperature in high-pressure vanadium, and could lead us to the next breakthrough in superconducting materials."
Yang Ding | EurekAlert!
Nanostructures taste the rainbow
29.06.2017 | California Institute of Technology
X-ray photoelectron spectroscopy under real ambient pressure conditions
28.06.2017 | National Institutes of Natural Sciences
Computer scientists use wave packet theory to develop realistic, detailed water wave simulations in real time. Their results will be presented at this year’s SIGGRAPH conference.
Think about the last time you were at a lake, river, or the ocean. Remember the ripples of the water, the waves crashing against the rocks, the wake following...
An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.
Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...
Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.
Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...
Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.
As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...
Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.
With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...
19.06.2017 | Event News
13.06.2017 | Event News
13.06.2017 | Event News
29.06.2017 | Physics and Astronomy
29.06.2017 | Life Sciences
29.06.2017 | Health and Medicine