Order, Disorder and the Entropic Bond: The Truth About Entropy

Sharon Glotzer, University of Michigan

An informal pre-seminar chat with the speaker, to which all are invited, will be held at at 3:30 p.m.

Abstract: Entropy is typically associated with disorder; yet, the counterintuitive notion that particles with no interactions other than excluded volume might self-assemble from a fluid phase into an ordered crystal has been known since the mid-20th century. First predicted for rods, and then spheres, the thermodynamic ordering of hard particle shapes by nothing more than crowding is now well established. In recent years, surprising discoveries of entropically ordered colloidal crystals of extraordinary structural complexity have been predicted by computer simulation and observed in the laboratory. Colloidal quasicrystals, clathrate structures, and structures with large and complex unit cells typically associated with metal alloys can all self-assemble from disordered phases of identical nanoparticles due solely to entropy maximization. In this talk, we show how entropy alone can produce order and complexity beyond that previously imagined.  We introduce the notion of the entropic bond, and show how methods used by the quantum community to predict atomic crystal structures can be used to predict entropic colloidal crystals.