MATERIALS SCIENCE AND CHEMISTRY

“If you want to understand function, study structure” (F. Crick). In the case of carbon, the very different properties of graphite, diamond, and carbon nanotubes can then be traced to different atomic arrangements. The elements provide a fruitful field of study in general. There are fewer than 100 stable elements, and trends can be identified more readily than in alloys with infinitely many compositions. He we describe cluster, amorphous, and liquid phases of the group 15 elements bismuth and antimony using molecular dynamics simulations based on density functional theory.

Rewritable optical storage media, such as the digital versatile disk (DVD-RW) and Blu-Ray Disc, are based on the extremely rapid and reversible crystallization of amorphous “bits” in thin polycrystalline layers of special alloy materials. The ultimate limit to the speed (and therefore usefulness) of such devices is the speed of crystallization of the amorphous structure, and the nature of the process has been the subject of much speculation. Insight is provided by simulations of crystallization of an amorphous alloy of germanium, antimony, and tellurium (GST) that is widely used as a component of commercial optical memories.