RT Journal Article
T1 Large attractive depletion interactions in soft repulsive-sphere binary mixtures
A1 Cinacchi, Giorgio
A1 Martínez-Ratón, Yuri
A1 Mederos, Luis
A1 Navascués, Guillelmo
A1 Tani, Alessandro
A1 Velasco, Enrique
AB We consider binary mixtures of soft repulsive spherical particles and calculate the depletion interaction between two big spheres mediated by the fluid of small spheres, using different theoretical and simulation methods. The validity of the theoretical approach, a virial expansion in terms of the density of the small spheres, is checked against simulation results. Attention is given to the approach toward the hard-sphere limit and to the effect of density and temperature on the strength of the depletion potential. Our results indicate, surprisingly, that even a modest degree of softness in the pair potential governing the direct interactions between the particles may lead to a significantly more attractive total effective potential for the big spheres than in the hard-sphere case. This might lead to significant differences in phase behavior, structure, and dynamics of a binary mixture of soft repulsive spheres. In particular, a perturbative scheme is applied to predict the phase diagram of an effective system of big spheres interacting via depletion forces for a size ratio of small and big spheres of 0.2; this diagram includes the usual fluid-solid transition but, in the soft-sphere case, the metastable fluid-fluid transition, which is probably absent in hard-sphere mixtures, is close to being stable with respect to direct fluid-solid coexistence. From these results, the interesting possibility arises that, for sufficiently soft repulsive particles, this phase transition could become stable. Possible implications for the phase behavior of real colloidal dispersions are discussed.
PB American Institute of Physics
SN 0021-9606 (Print)
SN 1089-7690 (Online)
YR 2007
FD 2007-12-07
LK https://hdl.handle.net/10016/6991
UL https://hdl.handle.net/10016/6991
LA eng
NO 12 pages, 8 figures.-- PACS nrs.: 82.70.Dd.-- ArXiv pre-print available at: http://arxiv.org/abs/0706.1633v2
NO MIUR (Italy) and Ministerio de Educación y Ciencia (Spain) are thanked for financial support under the 2005 Binational Integrated Program. Y.M.-R. was supported by a Ramón y Cajal Research Contract. This work is part of the research projects PRIN "Energy and Charge Transfers at Molecular Level" of MIUR (Italy), MOSAICO (Nos. FIS2005-05243-C02-01 and FIS2004-05035-C03-02) of the Ministerio de Educación y Ciencia (Spain), and of Comunidad Autónoma de Madrid (Spain) (No. S-0505/ESP-0299).
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RD 1 sept. 2024