# Difference between revisions of "Quasicrystalline order in self-assembled binary nanoparticle superlattices"

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== Key Points == | == Key Points == | ||

− | Equilibrium phase transformations are ubiquitous in nature. Because of their complexity, it is often useful to focus on the 'simple' case of hard spheres, whose equilibrium phase diagram is dictated purely on entropic grounds. For monodisperse Brownian spheres with purely hard-sphere interactions, volume fraction is the only control parameter: for small volume fractions, the system is fluid-like; for intermediate volume fractions (between ~49% and 55%), a fluid and crystal phase coexist; for volume fractions larger than ~55%, up to the maximum FCC packing fraction of ~74%, the system is crystalline. | + | Equilibrium phase transformations are ubiquitous in nature. Because of their complexity, it is often useful to focus on the 'simple' case of hard spheres, whose equilibrium phase diagram is dictated purely on entropic grounds. For monodisperse Brownian spheres with purely hard-sphere interactions, volume fraction is the only control parameter: for small volume fractions, the system is fluid-like; for intermediate volume fractions (between ~49% and 55%), a fluid and crystal phase coexist; for volume fractions larger than ~55%, up to the maximum FCC packing fraction of ~74%, the system is crystalline. For binary systems consisting of particles of two different sizes, the equilibrium phase diagram is much richer (e.g. see "Entropy-driven formation of a superlattice in a hard-sphere binary mixture" by Daan Frenkel's group in 2003), with three control parameters now - the volume fraction of each size particle, and the relative size difference between them. Further complexity develops in the equilibrium phase diagram with deviations from hard sphere behavior, such as the incorporation of van der Waals, Coulombic, and dipolar interactions. |

## Revision as of 20:12, 4 November 2009

Original entry: Sujit S. Datta, APPHY 225, Fall 2009.

## Reference

D. V. Talapin, E. V. Schevchenko, M. I. Bodnarchuk, X. Ye, J. Chen, and C. B. Murray, *Nature* **461,** 964 (2009).

## Keywords

quasicrystal, self-assembly, packing

## Key Points

Equilibrium phase transformations are ubiquitous in nature. Because of their complexity, it is often useful to focus on the 'simple' case of hard spheres, whose equilibrium phase diagram is dictated purely on entropic grounds. For monodisperse Brownian spheres with purely hard-sphere interactions, volume fraction is the only control parameter: for small volume fractions, the system is fluid-like; for intermediate volume fractions (between ~49% and 55%), a fluid and crystal phase coexist; for volume fractions larger than ~55%, up to the maximum FCC packing fraction of ~74%, the system is crystalline. For binary systems consisting of particles of two different sizes, the equilibrium phase diagram is much richer (e.g. see "Entropy-driven formation of a superlattice in a hard-sphere binary mixture" by Daan Frenkel's group in 2003), with three control parameters now - the volume fraction of each size particle, and the relative size difference between them. Further complexity develops in the equilibrium phase diagram with deviations from hard sphere behavior, such as the incorporation of van der Waals, Coulombic, and dipolar interactions.