Article

Self-assembly of a colloidal interstitial solid with tunable sublattice doping.

Soft Condensed Matter, Debye Institute for NanoMaterials Science, Utrecht University, Utrecht, the Netherlands.
Physical Review Letters (Impact Factor: 7.73). 10/2011; 107(16):168302. DOI: 10.1103/PhysRevLett.107.168302
Source: PubMed

ABSTRACT We determine the phase diagram of a binary mixture of small and large hard spheres with a size ratio of 0.3 using free-energy calculations in Monte Carlo simulations. We find a stable binary fluid phase, a pure face-centered-cubic (fcc) crystal phase of the small spheres, and binary crystal structures with LS and LS(6) stoichiometries. Surprisingly, we demonstrate theoretically and experimentally the stability of a novel interstitial solid solution in binary hard-sphere mixtures, which is constructed by filling the octahedral holes of an fcc crystal of large spheres with small spheres. We find that the fraction of octahedral holes filled with a small sphere can be completely tuned from 0 to 1. Additionally, we study the hopping of the small spheres between neighboring octahedral holes, and interestingly, we find that the diffusion increases upon increasing the density of small spheres.

0 Bookmarks
 · 
91 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: We present the phase diagram of hard snowman-shaped particles calculated using Monte Carlo simulations and free energy calculations. The snowman particles consist of two hard spheres rigidly attached at their surfaces. We find a rich phase behavior with isotropic, plastic crystal, and aperiodic crystal phases. The crystalline phases found to be stable for a given sphere diameter ratio correspond mostly to the close packed structures predicted for equimolar binary hard-sphere mixtures of the same diameter ratio. However, our results also show several crystal-crystal phase transitions, with structures with a higher degree of degeneracy found to be stable at lower densities, while those with the best packing are found to be stable at higher densities.
    The Journal of Chemical Physics 07/2012; 137(4):044507. · 3.12 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The densest binary sphere packings in the α-x plane of small to large sphere radius ratio α and small sphere relative concentration x have historically been very difficult to determine. Previous research had led to the prediction that these packings were composed of a few known "alloy" phases including, for example, the AlB(2) (hexagonal ω), HgBr(2), and AuTe(2) structures, and to XY(n) structures composed of close-packed large spheres with small spheres (in a number ratio of n to 1) in the interstices, e.g., the NaCl packing for n=1. However, utilizing an implementation of the Torquato-Jiao sphere-packing algorithm [Torquato and Jiao, Phys. Rev. E 82, 061302 (2010)], we have discovered that many more structures appear in the densest packings. For example, while all previously known densest structures were composed of spheres in small to large number ratios of one to one, two to one, and very recently three to one, we have identified densest structures with number ratios of seven to three and five to two. In a recent work [Hopkins et al., Phys. Rev. Lett. 107, 125501 (2011)], we summarized these findings. In this work, we present the structures of the densest-known packings and provide details about their characteristics. Our findings demonstrate that a broad array of different densest mechanically stable structures consisting of only two types of components can form without any consideration of attractive or anisotropic interactions. In addition, the structures that we have identified may correspond to currently unidentified stable phases of certain binary atomic and molecular systems, particularly at high temperatures and pressures.
    Physical Review E 02/2012; 85(2 Pt 1):021130. · 2.31 Impact Factor

Full-text (2 Sources)

View
50 Downloads
Available from
May 30, 2014

Laura Filion