Effect of inter-species selective interactions on the thermodynamics and nucleation free-energy barriers of a tessellating polyhedral compound

The phase behavior and the homogeneous nucleation of an equimolar mixture of octahedra and cuboctahedra are studied using thermodynamic integration, Gibbs-Duhem integration, and umbrella sampling simulations. The components of this mixture are modeled as polybead objects of equal edge lengths so tha...

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Bibliographic Details
Published in:The Journal of chemical physics 2016-12, Vol.145 (21), p.211903-211903
Main Author: Escobedo, Fernando A.
Format: Article
Language:English
Subjects:
CESIUM CHLORIDES
Computer simulation
CRYSTAL STRUCTURE
Filling
FREE ENERGY
INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY
INTERACTIONS
Long range order
Metastable state
METASTABLE STATES
NUCLEATION
Physics
Supersaturation
THERMODYNAMICS
Variation
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Summary:The phase behavior and the homogeneous nucleation of an equimolar mixture of octahedra and cuboctahedra are studied using thermodynamic integration, Gibbs-Duhem integration, and umbrella sampling simulations. The components of this mixture are modeled as polybead objects of equal edge lengths so that they can assemble into a space-filling compound with the CsCl crystal structure. Taking as reference the hard-core system where the compound crystal does not spontaneously nucleate, we quantified the effect of inter-species selective interactions on facilitating the disorder-to-order transition. Facet selective and facet non-selective inter-species attractions were considered, and while the former was expectedly more favorable toward the target tessellating structure, the latter was found to be similarly effective in nucleating the crystal compound. Ranges for the strength of attractions and degree of supersaturation were identified where the nucleation free-energy barrier was small enough to foretell a fast process but large enough to prevent spinodal fluctuations that can trap the system in dense metastable states lacking long-range order. At those favorable conditions, the tendency toward the local orientational order favored by packing entropy is amplified and found to play a key role seeding nuclei with the CsCl structure.
ISSN:0021-9606
1089-7690
DOI:10.1063/1.4953862