Researchers Demonstrate Template for Development of Extended Metal-Anion Arrays
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experiment “are largely fortuitous.” By contrast, the method developed by McCurdy and his team allows the calculation of a highly accurate wave function for the outgoing state that can be interrogated for details of the incoming state and interaction in the same way an experimenter would interrogate a physical system. The researchers acknowledge important advances made earlier by others such as Igor Bray and Andres Stelbovics, whose methods could give the total cross section for ionization of a scattering reaction but could not give specifics such as the directions or energies of outgoing electrons. By contrast, said Thomas Rescigno, a staff physicist at Livermore Lab, “Our work produces absolute answers at the ultimate level of detail.” Comparisons with real scattering experiments, such as those recently published by J. Röder et al., who scattered incoming 17.6-eV electrons from hydrogen atoms and measured the angles and energies of the outgoing electrons, prove the accuracy of the new method. The experimental data points match the graph of the cross sections calculated by McCurdy’s research team. “Even if the specific methods have changed, quantum chemistry was founded when the helium atom with two bound electrons was solved—it showed that these problems were, in principle, solvable,” McCurdy said. “What we have done is analogous. The details of our method probably won’t survive, but we’ve taken a big step toward treating ionizing collisions of electrons with more complicated atoms and molecules.” The authors conclude that the same computing power and tools necessary for investigating the complexity of increasingly larger systems are also needed “to answer a basic physics question for one of the simplest systems imaginable in physics and chemistry.”
Researchers Demonstrate Template for Development of Extended Metal-Anion Arrays Researchers at the University of New Orleans have synthesized a set of perovskite-related, layered copper-oxyhalides, (CuX)LaNb2L7, X = Cl and Br), where a copper-halide network was assembled within a double-layered perovskite host (see figure). The synthetic approach that T.A. Kodenkandath and his colleagues of J.B. Wiley’s research group describe in the December 1999 issue of the Journal of the American Chemical Society demonstrates how host structures can be used as templates in the directed low-temperature
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An idealized structure of (CuX)LaNb2O7. The small dark balls are copper surrounding the large balls, which are X (Cl, Br).
(700°C. The researchers concluded that their method of assembling metal-anion networks may lead to new rationally designed materials as applied to nonmolecular systems.
Jackie Ying, an associate professor of chemical engineering at the Massachusetts Institute of Technology, has created a barium hexaaluminate (BHA) catalyst that could make it easier to burn methane while drastically cutting emissions of pollutants from natural-gas power plants. Her research team’s challenge was
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