title: Structural and dynamical analysis of monodisperse and polydisperse colloidal systems.
abstract: We present a semigrand ensemble Monte Carlo and Brownian dynamics simulation study of structural and dynamical properties of polydisperse soft spheres interacting via purely repulsive power-law potentials with a varying degree of "softness." Comparisons focus on crystal and amorphous phases at their coexistence points. It is shown through detailed structural analysis that as potential interactions soften, the "quality of crystallinity" of both monodisperse and polydisperse systems deteriorates. In general, polydisperse crystalline phases are characterized by a more ordered structure than the corresponding monodisperse ones (i.e., for the same potential softness). This counter-intuitive feature originates partly from the fact that particles of different sizes may be accommodated more flexibly in a crystal structure and from the reality that coexistence (osmotic) pressure is substantially higher for polydisperse systems. These trends diminish for softer potentials. Potential softness eventually produces substitutionally disordered crystals. However, substitutional order is apparent for the hard-spherelike interactions. Diffusionwise, crystals appear quite robust with a slight difference in the vibrational amplitudes of small and large particles. This difference, again, diminishes with potential softness. Overcrowding in amorphous polydisperse suspensions causes "delayed" diffusion at intermediate times.
authors.affiliation: Molecular Thermodynamics and Modeling of Materials Laboratory, Institute of Physical Chemistry, National Center for Scientific Research Demokritos, GR-153 10 Aghia Paraskevi Attikis, Greece.
authors.forename: Marianna
authors.initials: M
authors.lastname: Yiannourakou
authors.forename: Ioannis G
authors.initials: IG
authors.lastname: Economou
authors.forename: Ioannis A
authors.initials: IA
authors.lastname: Bitsanis
mesh_terms: D003102:Colloids / Q000737:chemistry*; D003460:Crystallization; D004058:Diffusion; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D009010:Monte Carlo Method; D010316:Particle Size; D013535:Suspensions / Q000737:chemistry
chemical_list: D003102:Colloids; D013535:Suspensions