Researchers have long hoped that computer simulations of how atoms interact would allow them to design useful new materials from scratch. But the physics of atomic interactions rapidly becomes so complex that using it to predict the properties and performance of real-world materials has proved extremely difficult. Ju Li, an assistant professor of materials science and engineering, has developed new algorithms to model some of the hardest-to-understand phenomena in his field: the mechanical properties of complex, nanostructured materials. In one model, illustrated above, Li shows that combining nanoscale layers of amorphous copper zirconium and crystalline copper yields a material as much as ten times as strong as copper, without making it too brittle to be useful. In the crystalline region in the middle, atoms in one plane slip by atoms in neighboring planes, allowing the material to easily change shape under stress. The outer amorphous layers don't change shape that way, so they keep the planes from slipping too far. Li's collaborators have already shown experimentally that this structure results in a strong but malle­able material.

Well-aligned crystalline copper atoms are sandwiched between two areas of amorphous copper.

--Kevin Bullis