Assembly of body-centered cubic crystals in hard spheres |
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Authors: | W -S Xu Z -Y Sun L -J An |
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Institution: | State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, PRC. |
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Abstract: | We investigate the crystallization of monodisperse hard spheres confined by two square patterned substrates (possessing the
basic character of the body-centered cubic (bcc) crystal structure) at varying substrate separations via molecular dynamics
simulation. Through slowly increasing the density of the system, we find that crystallization under the influence of square
patterned substrates can set in at lower densities compared with the homogeneous crystallization. As the substrate separation
decreases, the density, where crystallization occurs (i.e., pressure drops), becomes small. Moreover, two distinct regimes are identified in the plane of bcc particle fraction and
density for the separation range investigated. For large substrate separations, the bcc particle fraction displays a local
maximum as the density is increased, and the resulting formed crystals have a polycrystalline structure. However, and more
importantly, another situation emerges for small substrate separations: the capillary effects (stemming from the presence
of two substrates) overwhelm the bulk driving forces (stemming from the spontaneous thermal fluctuations in the bulk) during
the densification, eventually resulting in the formation of a defect-free bcc crystal (unstable with respect to the bulk hard-sphere
crystals) by using two square patterned substrates. |
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