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The Laboratory
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Synthesizing noble metals under extreme conditions
Laboratory scientists, in collaboration with researchers from the Carnegie Institution of Washington and the Atomic Weapons Establishment in England, have synthesized a novel class of nitrides made from noble metals under extreme conditions. Noble metals are those that do not easily form compounds with other elements.
Using a diamond anvil cell to create high pressures and a laser to create high temperatures, the researchers made the first bulk nitride of the noble metal iridium. By combining experimental results with first-principle theoretical modeling, the scientists also have determined the structure of the known nitride of platinum as well as its bulk modulus (a measure of the material hardness). The semiconductor industry currently uses titanium nitrides because of their strength and durability. These new nitrides may prove to be even more durable than titanium.
“This work extends the scientific understanding of platinum and iridium nitrides,” says lead author Jonathan Crowhurst of Livermore’s Chemistry and Materials Science Directorate. “Demonstrating that these compounds exist and determining at least some of their physical properties should inspire the development of large-scale synthesis techniques to take advantage of their unusual properties.” Other Livermore authors include Babak Sadigh, Cheryl Evans, James Ferreira, and Art Nelson. The research is presented in the March 3, 2006, issue of Science.
Contact: Jonathan Crowhurst (925) 422-1945 (crowhurst1@llnl.gov).

The evolution of icy moons
Researchers from the Laboratory, Kyushu University in Japan, and the U.S. Geological Survey found a “creep” or flow mechanism in a high-pressure form of ice that is affected by the grain size of the ice. High-pressure phases of ice are major components of the giant icy moons in the outer solar system. The convective flow of ice in the interiors of these moons has controlled their evolution and present-day structure.
Experiments were conducted in Livermore’s Experimental Geophysics Laboratory under the conditions of pressure, temperature, stress, and grain size that mimic those in the deep interiors of large icy moons. Using a cryogenic scanning electron microscope, the researchers observed and measured creep as a function of grain size in a high-pressure phase of ice called “ice II.” They proved that this new creep mechanism was related to grain size, something that previously had only been examined theoretically.
“These new results show that the viscosity of a deep icy mantle is much lower than we previously thought,” says William Durham, a geophysicist in Livermore’s Energy and Environment Directorate. The researchers conclude that it is likely the ice deforms by the creep mechanism in the interior of icy moons when the grains are up to a centimeter in size. “This newly discovered creep mechanism will change our thinking of the thermal evolution and internal dynamics of medium- and large-size moons of the outer planets in our solar system,” says Durham. “The thermal evolution of these moons can help us explain what was happening in the early solar system.” The team’s research appeared in the March 3, 2006, issue of Science.
Contact: William Durham (925) 422-7046 (durham1@llnl.gov).

Oxygen breathed life into biological evolution
New research shows that many of the complex biochemical networks that humans and other advanced organisms depend on for their existence could not have evolved without oxygen. Livermore postdoctoral researcher Jason Raymond and Daniel Segrè of Boston University, who holds a joint appointment in Livermore’s Biosciences Directorate, used computer simulations to study the effect of oxygen on metabolic networks, which are the biochemical systems that enable organisms to convert food and nutrients into life-sustaining energy. Their analysis shows that the largest and most complex networks—those found in humans and other advanced organisms—require the presence of molecular oxygen. The team’s research appeared in the March 24, 2006, issue of Science.
Raymond and Segrè calculated the number of possible combinations of the thousands of enzymes and chemicals involved in all known metabolic reactions across the tree of life and came up with a “virtually limitless” number—10 to the 16,536th power. Simulating that many networks would be an impossible task even for Livermore’s powerful supercomputers. To make the project manageable, the researchers used a statistical technique called Monte Carlo to randomly sample and simulate about 100,000 networks. “We found that all the types of networks fell into four different clusters of increasing size and connectivity,” says Raymond. “In networks within the largest clusters, molecular oxygen was always present. Oxygen is the high-energy reactant that is needed for the growth of large, complex, multicellular organisms. Life as we know it was kick-started a few billion years ago by the oxygen-producing microbes.”
The new findings also may imply that oxygen would be a good proxy for the search for intelligent life elsewhere in the universe. Furthermore, Raymond and Segrè’s findings suggest that additional evolutionary secrets might be uncovered through the study of metabolic networks.
Contact: Jason Raymond (925) 423-6507 (raymond20@llnl.gov).

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UCRL-52000-06-6 | June 1, 2006