Comparison of metals and colloids: short-range order in liquid state and crystal nucleation

Abstract

Colloids are investigated by Ultra-Small-Angle-X-ray-Scattering (USAXS) with respect to the topological short range order in metastable liquid state. A preference of icosahedral short range order is found quite analogous to the short range order in undercooled melts of pure metals. From the time evolution of the structure factor measured by USAXS during crystallization the homogeneous nucleation rate is determined. From the homogeneous nucleation rate the solid-liquid interfacial energy is inferred. A Turnbull plot of interfacial enery as a function of the difference of chemical potential of solid and liquid of colloidal systems is constructed and compared with early results by Turnbull obtained from undercoling experiments on pure metals and more recent results of MD simulations on pure metals. The dimensionless interfacial energy of colloidal systems is found to be by a factor of 6-7 smaller than the dimensionless interfacial energy of systems of hard matter as metals.