Disclaimer

In a recent paper, Tanja Schilling and I reported that ellipsoids at high densities don’t make a crystal where all particles point in the same direction. The more stable crystal has two main directions of orientation, which alternate in layers. This came out of Monte Carlo simulations.

The color code in these pictures helps distinguish the two ellipsoid orientations present in the system.

I then worked with Tanja Schilling’s Diploma student Marc Radu (now her Ph.D. student), who did simulations to calculate free-energy* differences between various crystal structures. The associated publication is here.

* Free energy is a measure of how unstable a phase is (e.g. a certain crystal structure, or a liquid). For example, superheated water is unstable compared to vapor, so its free energy is higher than that of the vapor under the same conditions (temperature, pressure, ...).