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Prediction of Cooling Rate Dependent Ordering in the Metallic Glass Transition

Prediction of the development of structural ordering associated with the glass transition in metallic liquids has eluded scientists since the discovery of metallic glasses in 1960. Indeed, this issue presents a fundamental problem of incommensurate time scales, since the cooling rates generally required for the formation of a metallic glass from a liquid (103 K/s) are too high to allow for direct experimental measurement of structural dynamics, but too low to permit direct simulation through molecular dynamics methods (generally limited to 108 K/s).

Finding the Right Stuff

NaAs has been discovered as an effective solvent for RFeAsO (R = rare earth) superconducting compounds and enables the growth of sizeable high quality single crystals by the solution method at ambient pressure. Solution growth is a versatile, rapid technique for growth of single crystals. Much like preparing rock candy, the technique relies on having the right solution that dissolves and then precipitates the compound of interest.

Chemical Synthesis of Magnetic Molecules

The discovery that transition-metal clusters can behave like tiny “magnets,” i.e. single-molecule magnets (SMMs), opens up the opportunity for their applications in information storage, quantum computing, and molecular spintronics devices. A major objective of our synthetic project is on the design and synthesis of such molecular nanomagnets, based on inorganic polyoxometalate ligands given the rigidity (which infers predictability) and diversity (which allows rational chemical design) of their ligand environments.

Metamaterials: Giving light another new twist, chirality

After years of doubt, the scientific community now embraces the almost paradoxical properties of metamaterials, also known as negative index materials (NIMs). The unusual properties of fabricated NIMs include perfect lensing (beating the diffraction limit for electromagnetic waves), zero reflectance, and negative Snell’s law angles. Acceptance of these phenomena has come with recent design, fabrication, demonstration, and detailed first principles simulations for operation at microwave and THz frequencies from the Ames Laboratory group.

Repulsive Casimir Force in Chiral Metamaterials

First predicted by distinguished Dutch physicist, H.B.G. Casimir in 1948, the Casimir force arises when two uncharged, parallel metallic plates are brought in close proximity. Noticeable at a distance of a few microns, this attracting force becomes dominant at a length scale of tens of nanometers. Classically, no force exists between the plates; the Casimir force is proportional to the surface’s area, a consequence of the quantum nature of the electromagnetic field. Not restricted to parallel plates, the Casimir force exists between any two objects for microscopic separations.


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