A stable cluster of aluminum atoms, Al13, acts as a single entity in chemical reactions, demonstrating properties similar to those of a halogen, reports a research team led by A. Welford Castleman Jr., the Evan Pugh Professor of Chemistry and Physics and the Eberly Family Distinguished Chair in Science at Penn State, in a paper to be published in the 2 April 2004 issue of the journal Science. Experimental results and theoretical calculations indicate that the cluster chemically resembles a "superhalogen" atom, retaining its properties during the reaction and in reaction products. Other team members include Denis E. Bergeron of the Penn State departments of chemistry and physics and Shiv N. Khanna of the Virginia Commonwealth University department of Physics. One implication of the research is the possibility of using such clusters as building blocks in nanoscale fabrication.
Figure 1: Charge density map of the highest occupied molecular orbital for the Al13I- cluster. Note the preservation of Al13I- icosahedral geometry, and the localized charge density on the aluminum cluster moiety. Color code: blue=aluminum; red=iodine.
Figure 2: Top Image: Lowest energy structure for Al13I-. Color code: blue=aluminum; red=iodine
Bottom Image: Charge density map of the highest occupied molecular orbital for Al13I-. Color code: blue=aluminum; red=iodine
The project focused on experimental evidence of the existence of a very stable cluster anion, Al13I-, prepared by the gas-phase reaction of aluminum clusters with HI gas. Mass spectrometric analysis indicated that the reaction produced relatively few products, the most abundant corresponding to Al13I-. Energy calculations to determine the bonding mechanism between the aluminum cluster and the iodine atom indicate that the extra electron is localized on the Al13 cluster, meaning that the cluster maintains its integrity throughout the reaction. Because the cluster has a greater electron affinity in the compound, or attraction to the free electron, than does iodine, it can be considered a "superhalogen."
"One of the themes of our research is using the clusters as building blocks for new nanoscale materials," says Castleman. "In many cases, people have worked from the top down; that is, subdividing matter to get it smaller and smaller. Were trying to work with atoms and molecules and put them together--working our way from the bottom up. If we can retain the properties of aggregates, as we put them together, perhaps we will be able to construct new nanoscale materials." The key to using the aggregates as building blocks is that they retain their individual properties during the reaction and do not coalesce into a large aggregate.
Barbara K. Kennedy | Penn State
Research finds new molecular structures in boron-based nanoclusters
13.07.2018 | Brown University
3D-Printing: Support structures to prevent vibrations in post-processing of thin-walled parts
12.07.2018 | Fraunhofer-Institut für Produktionstechnologie IPT
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
13.07.2018 | Event News
13.07.2018 | Materials Sciences
13.07.2018 | Life Sciences