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!
Astronomers find unexpected, dust-obscured star formation in distant galaxy
24.03.2017 | University of Massachusetts at Amherst
Gravitational wave kicks monster black hole out of galactic core
24.03.2017 | NASA/Goddard Space Flight Center
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
27.03.2017 | Earth Sciences
27.03.2017 | Life Sciences
27.03.2017 | Life Sciences