"The reason I think that a preponderance of our papers are in this issue is that it deals with fluids and other soft condensed materials in confinement, in various matrices, and that is a really natural area for neutron scattering investigations. It is a strong area within our science program," explained Mike Simonson, Chemicals and Engineering Division chief in the Neutron Sciences Directorate.
A monthly, peer-reviewed scientific journal published by the Institute of Physics, the journal reports on all areas of condensed matter physics, including soft matter and nanostructures.
Eugene Mamontov, lead instrument scientist on the backscattering spectrometer BASIS, said "neutron scattering is indispensible in the field of the dynamics of water and glass-forming liquids." Mamontov is first author on two of the papers, and a participant on a third. "It's fine research along the lines of 'how this physics works,'" he said.
The primary instruments for water dynamics and glass-forming liquids studies are the SNS's BASIS (beam line 2) and the Neutron Spin Echo Spectrometer (beam line 15). "That is it, primarily: low energy transitions in BASIS, large scale structures in SANS, and a combination in Spin Echo and Spin Echo SANS," Simonson said
"We are hoping that NOMAD will have a strong role to play in this area, as well. The studies of local structures in liquids will be a particularly strong feature of the science program on NOMAD and as we get the user program going, NOMAD will make a real contribution.
"The primary goal of this particular research is really to understand the fundamental physics behind why a liquid would freeze or not freeze under certain conditions," said Simonson, who has spent his whole career studying water.
"If some liquids are cooled very quickly, then instead of crystallizing into ice, they actually become a glass. In fact all of our window pane glass is basically material that has been heated up and then liquefied and then cooled so quickly that it made a glass, rather than a crystal. Now this material is a lot tougher than a crystalline material would be. So it has some really good practical applications."
Studies of water are particularly intriguing. "Water is a remarkable material. Compared with other 'simple liquids', it remains liquid over a wide temperature range, and probably comes as close as any pure liquid to being a 'universal' solvent," Simonson explained.
"Differently from most liquids, solid water (ice) is less dense than liquid water; this keeps large bodies of water from freezing solid to the bottom in winter and allows aquatic life to survive. The presence of water is taken as one of the indicators that life may be possible on other planets, given its unique physical and chemical properties and its critical role in biology.
"Since it is a cornerstone of life, it becomes crucial to understand complex systems where water plays a big role in the overall function of the system."
Another researcher who brought his work to ORNL, Sow-Hsin Chen, is a senior professor at MIT who has spent his career studying supercooled water, water that is cooled below the freezing point, but does not freeze; and water that's confined in very tight pores, which changes its properties. Two young NScD researchers whose work also appears in the special issue, Wei-Ren Chen and Shull Fellow Yang Zhang, studied under Chen at MIT.
"He has furthered the understanding of the molecular interactions that drive water's very unique behavior," Simonson said. "This is very much on the fundamental side of the spectrum, understanding complex systems where water plays a big role. But since water is everywhere, it has applications everywhere.
"We might find a new material with a tremendous increase in heat capacity, for example. Water is one of the best thermal transport mediums that we have. It is used to cool just about everything. We add a little antifreeze to water and it changes the properties and makes it an even better heat transfer fluid. What if there is something better than antifreeze? "
Future researchers could conceivably tailor water to be a better solvent for molecules that don't dissolve in water. They could extract valuable minerals from water, such as uranium from seawater. "In principle it can be done," Simonson says, "but water hangs onto it so tightly and the uranium is so dilute that it becomes impractical, compared with mining.
"But if we really understood how it was in there, maybe we could do that separation better."
"There is a huge economic impact from being able to do a separation without having to do a distillation," Simonson said. "Distillation is about the most expensive way to separate two components from each other, because one has to pump in so much heat. If you have a membrane, or a sieve, or precipitation, or just about any other process, it could potentially be more energy efficient than just doing a distillation."
The six ORNL research articles published in "Dynamics of Water and Glass Forming Liquids," Journal of Physics Condensed Matter, January 26, are
Eugene Mamontov, A De Francesco, F Formisano, A Laloni, L Sani, B M Leu, A H Said and Alexander I Kolesnikov, "Water dynamics in a lithium chloride aqueous solution probed by Brillouin neutron and x-ray scattering." doi:10.1088/0953-8984/24/6/064104
Eugene Mamontov, H O'Neill, Q Zhang, Wang Wang and D J Wesolowski,"Common features in microscopic dynamics of hydration water on organic and inorganic surfaces." doi:10.1088/0953-8984/24/6/064104
Kunlun Hong, Yun Liu, Lionel Porcar, Dazhi Liu, Carrie Y Gao, Gregory S Smith, Kenneth W Herwig, Sheng Cai, Xin Li, Bin Wu, Wei-Ren Chen and Li Liu, "Structural response of polyelectrolyte dendrimer toward the molecular protonation: the inconsistence revealed by SANS and NMR." doi:10.1088/0953-8984/24/6/064104
Yang Zhang, Madhusudan Tyagi, Eugene Mamontov and Sow-Hsin Chen, "Quasi-elastic neutron scattering studies of the slow dynamics of supercooled and glassy aspirin." doi:10.1088/0953-8984/24/6/064104
Peter Falus, Lionel Porcar, Emiliano Fratini, Wei-Ren Chen, Antonio Faraone, Kunlun Hong, Piero Baglioni and Yun Liu, "Distinguishing the monomer to cluster phase transition in concentrated lysozyme solutions by studying the temperature dependence of the short-time dynamics." doi:10.1088/0953-8984/24/6/064104
Xin Li, Bin Wu, Yun Liu, Roger Pynn, Chwen-Yang Shew, Gregory S Smith, Kenneth W Herwig, Jack L Robertson, Wei-Ren Chen and Li Liu," Contrast variation in spin-echo small angle neutron scattering." doi:10.1088/0953-8984/24/6/064104