Most solids expand when heated, a familiar phenomenon with many practical implications. Among the rare exceptions to this rule, the compound zirconium tungstate stands out by virtue of the enormous temperature range over which it exhibits so-called "negative thermal expansion," contracting as it heats up and expanding as it cools, and because it does so uniformly in all directions.
While engineers are already pursuing practical applications in areas ranging from electronics to dentistry, physicists have had a hard time explaining exactly what causes zirconium tungstate to behave in such a bizarre manner. Now, a team of researchers at the University of California, Santa Cruz, and other institutions has reported new insights into the atomic interactions underlying this phenomenon. A paper describing their findings will be posted online on November 22 and will appear in the December 26 issue of the journal Physical Review Letters. "We have shown that a combination of geometrical frustration and unusual atomic motions are likely to be important to the negative thermal expansion in zirconium tungstate," said Zack Schlesinger, a professor of physics at UCSC.
Geometrical frustration sounds like something a high-school math student might feel, but is actually a rich area of research in physics and material science. In simple terms, geometrical frustration is like trying to tile a floor with pentagons--the shapes just wont fit together. In the case of zirconium tungstate, geometrical frustration comes into play during certain temperature-related vibrations of the compounds crystal lattice structure, the configuration of atomic bonds that holds the atoms together in a crystal.
Tim Stephens | EurekAlert!
Tune your radio: galaxies sing while forming stars
21.02.2017 | Max-Planck-Institut für Radioastronomie
Breakthrough with a chain of gold atoms
17.02.2017 | Universität Konstanz
Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...
The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.
The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...
Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...
Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".
Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...
13.02.2017 | Event News
10.02.2017 | Event News
09.02.2017 | Event News
21.02.2017 | Earth Sciences
21.02.2017 | Medical Engineering
21.02.2017 | Trade Fair News