Colloidal crystal-liquid Interface: Anisotropy, Free energy, and Structure

Investigation of the crystal--liquid interface is of central importance for understanding crystal growth, and nucleation. This interface is the most difficult to study experimentally because it is buried between two condensed phases. We use micron-size colloidal particles as models to visualize atomic processes of crystal growth. Because of their larger length and time scales, by optical microscopy, we can observe and even track the motion of the individual particles in three dimensions and time. This provides an excellent opportunity to study the crystal-liquid interface on the ``atomic'' level. We determine all thermodynamic properties of the system: pressure, the chemical potential, and the free energy density. We use interface fluctuations to determine the interfacial tension and its dependence on the crystal orientation, important parameters of crystal growth. Remarkably, the anisotropy of the interfacial tension that we find is very similar to that measured for real metallic crystals