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Madhu Menon
Understanding Nanostructures

by Jeff Worley & Robin Roenker

When it was discovered in the early 1990s, the carbon nanotube was heralded as the breakthrough material of the future. Lightweight and miniscule, yet hundreds of times stronger than steel, the nanotube's applications were thought to be endless.

Photo of Madhu MenonAnd so they still may be, as research on nanotubes continues. But the nanotube's potential pales in comparison to that of the nanowire, discovered in 1997, says Madhu Menon, associate director of the Center for Computational Sciences. The distinction: nanotubes are hollow, but nanowires are rod-shaped.

Nanowires share all of the alluring qualities of their hollow counterparts, and they have an added advantage: they are much more versatile. While the structures of nanotubes are limited—occurring in only three different forms (due to the specific ways in which atoms must be connected to produce them)—nanowires occur in possibly an infinite number of geometries.

"Because nanowires occur in so many shapes, there is much more flexibility in how you can manipulate them to fine-tune their electronic properties," Menon says. "Currently, there's much more interest in nanowires than in nanotubes."

Using his own quantum molecular dynamics computer program and parallelized supercomputers, Menon conducts computational simulations that allow him to identify and predict the optimal atomic structure of nanowires. Once the structures themselves are identified, Menon can then work to predict vital information about the nanostructures' physical properties, such as their electrical, or quantum, conductivity.

His computational prediction regarding the smallest possible silicone nano-wire was recently verified by experiment. "We predicted a few years back that it is possible to make a nanowire that is very small, between one and two nanometers in diameter; and recently a group in Hong Kong was able to make such a nanowire in the lab," Menon says.

His research also focuses on predicting the structure and properties of "unconventional magnetic materials"—a broad term referring to any non-metallic magnetic material. The recently discovered magnetic potential of pure carbon has opened the door to this new field of study. "Right now, we are working to predict whether or not these magnetic properties occur in other elemental structures," Menon says. "I believe they definitely can."

Ultimately, "the goal is to use nanotechnology to make devices," says Menon. From high-power computers to super-efficient and economical heat transfer systems and semiconductors, the future applications of nanotubes, nanowires and unconventional magnetic materials Menon is developing computationally have only begun to be imagined.

About Madhu Menon

Madhu Menon, who came to UK in 1991, is associate director of UK's Center for Computational Sciences. His research on condensed matter theory has frequently been featured in Physical Review Letters, one of the most prestigious journals in physics. In addition to his work on nanotubes, nanowires and unconventional magnetic materials, Menon also researches carbon fullerenes, silicon clathrates, complex hetero-atomic systems, and magnetism in transition metals.

Menon Research Team