Some solids naturally fluctuate between two structural forms; now researchers have followed such a transformation directly at atomic resolution in a copper sulphide nanorod. Understanding this process at the atomic scale might lead to the rational design of novel materials that exploit such transformations, such as memory-storage materials. Haimei Zheng and Paul Alivisatos at the Lawrence Berkeley National Laboratory in Berkeley, California, and their colleagues used high-resolution transmission electron microscopy to watch copper sulphide nanorods oscillate between two solid-phase structures when heated by an electron beam. The transition occurred just above room temperature, and the material oscillated a number of times before its structure reached a stable configuration. Defects in the material strongly influenced the dynamics of the transformation by partitioning the nanorod into different domains, each with a different oscillation frequency. Science 333,206-209 (2011)
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