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Computer Models Help Explain Bent Crystals
September 9, 2010

Blacksmiths make horseshoes by heating, beating and bending iron, but what’s happening to the metal’s individual atoms during such a process? Using computational modeling, Cornell researchers are gaining new insight into how atoms in crystals rearrange as the material is bent and shaped.

Such new ideas could lead to a better understanding of structural materials, from buildings to bridges, to make them less susceptible to tearing or breaking.

The researchers made computer-synthesized models of what such metals as aluminum and copper look like at the atomic level while being stretched, heated and cooled. They simulated how crystals, whose atoms start in a regular grid, transform as they are bent into different shapes.

The work was published in a recent edition of Physical Review Letters, a publication of the American Physical Society.

When a single crystal is bent, portions of the crystal shift and create defects in the lattice called dislocations. The researchers found that their crystals exhibited starkly contrasting properties depending on temperature.

When hot crystals were bent, the dislocations arranged into grain boundaries, which are the places where lattice planes suddenly tilt. At low temperatures, the dislocations formed self-similar, random patterns known as fractals.

The work was funded by the Department of Energy and the National Center for Supercomputing Applications.

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