Notable exceptions to this rule exist, the most famous one being the melting of ice. Recently, some experimentalists have discovered a number of other materials that have anomalous melting properties.
Measurements realized at a synchrotron facility (a ring in which electrons are accelerated) on a sodium crystal, which is archetype of a so-called ‘simple’ metal, have indicated that above a certain compression the sample begins to contract upon melting. This effect is so pronounced that it causes the melting temperature to decrease all the way down to room temperature! [Gregoriantz, et al., Physical Review Letters 2005]
Thanks to computer simulations of solids and liquids and to quantum mechanics calculations, an international research group from Belgium (Jean-Yves Raty, FNRS-University of Liège), Canada (Prof. Stanimir Bonev, Dalhousie University) and California (Dr Eric Schwegler, Lawrence Livermore National Laboratory), managed to reproduce the results of the experiments.
Researchers were surprise to discover that not only the sodium atoms were modified under pressure with a modification of their arrangement, but that the electrons themselves were transformed: the electronic cloud gets modified, the electrons sometimes get trapped into interstitial voids of the liquid and the bonds between atoms adopt some specific directions. This behavior is totally new in a liquid as one expects that metals get compacter with pressure, the ‘harder’ nuclei behaving as billiard balls in a quasi-uniform sea of electrons. Thanks to our simulations, we have shown that this new liquid is not a perfect metallic anymore and thus, even its color should change. Today, evidence is building from other calculations in the scientific group as well as experiments underway in various labs that the other seemingly simple metals in the periodic table may exhibit unusual melting as well.The results are published in next issue of Nature magazine (September 27th). "Electronic and structural transitions in dense liquid sodium"
Jean-Yves Raty , Eric Schwegler & Stanimir A. Bonev.
Didier Moreau | alfa
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...
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