Fractional crystallization of hard spheres

Fractional crystallization is crystal formation out of chemical mixtures or solutions. In this process, the growing crystal typically has a different composition than the fluid. This makes fractional crystallization an important method for separating or purifying substances based on differences in solubility. In geology, fractional crystallization is operating within the Earth’s crust and mantle during the formation of igneous rocks.

The simplest case of fractional crystallization in simulation is the crystallization of hard spheres. Praveen Bommineni, MAP student Nydia Varela-Rosales and Marco Klement in the group of Michael Engel now calculated the crystallization behavior of mixtures of hard spheres as a function of size-dispersity (composition) and packing fraction (density). The work was achieved using advanced statistical sampling to speed up simulation and access long times required for observing the crystallization phenomenon. The crystals discovered have relevance for the behavior of nanoparticles, micelles, and the structure of alloys and the elements.

Complex Crystals from Size-Disperse Spheres
P.K. Bommineni, N.R. Varela-Rosales, M. Klement, M. Engel
Physical Review Letters 122, 128005 (2019)