A density functional model for the binary crystal of hard spheres with vacancies

Singh, Sunil P. ; Das, Shankar P. (2007) A density functional model for the binary crystal of hard spheres with vacancies Journal of Chemical Physics, 126 (6). 064507_1-064507_10. ISSN 0021-9606

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Official URL: http://jcp.aip.org/resource/1/jcpsa6/v126/i6/p0645...

Related URL: http://dx.doi.org/10.1063/1.2431805


We study the stability of a binary mixture of hard spheres in the crystalline state in which a small fraction of lattice sites in the solid structure are vacant. The optimum vacancy concentration is obtained by minimizing the free energy of the inhomogeneous solid state. We use the modified weighted density functional approximation to compute the free energy. The necessary input for the theory is the thermodynamic properties of the homogeneous state of the mixture and is obtained from the solutions of the corresponding Percus-Yevick integral equations for the binary system. We compute the free energy for the crystal having two kinds of ordered structures in which (i) both the species lie in a disordered manner on a single face-centered-cubic lattice and (ii) each of the two species lie on a separate cubic lattice. Our theoretical model obtains equilibrium vacancy fraction of O(10-5) near the freezing point in both cases. The vacancy concentration decreases with the increase of density in both cases.

Item Type:Article
Source:Copyright of this article belongs to American Institute of Physics.
Keywords:Density Functional Theory; Vacancies (crystal); Crystal Structure; Free Energy; Thermodynamic Properties; Freezing
ID Code:93986
Deposited On:30 Jun 2012 12:33
Last Modified:30 Jun 2012 12:33

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