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
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Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
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Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
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For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
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An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
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A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
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