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Issue 41, 2007
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Physical properties of soft repulsive particle fluids

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Abstract

Molecular dynamics computer simulation has been applied to inverse power or soft-sphere fluids, in which the particles interact through the soft-sphere pair potential, ϕ(r) = ε(σ/r)n, where n measures the steepness or stiffness of the potential, and ε and σ are a characteristic energy and distance, respectively. The focus of the study is on very soft particles with n values down to 4 considered, at densities up to and along the fluid–solid co-existence density. It is shown that in the soft-particle limit the local structure is dominated by the lengthscale associated with the average nearest neighbour distance of a random structure, which is ∝ρ−1/3 and increasingly only very weakly dependent on n. This scaling is also manifest in the behaviour of the average energy per particle with density. The self-diffusion coefficient and shear viscosity are computed along the fluid–solid co-existence line as a function of n, for the first time. The product s steadily increases with softness for n < 10, whereas the modified Stokes–Einstein relationship of Zwanzig, s/ρ1/3, where ρ is the number density, is within statistics constant over the same softness range. This is consistent with our observation that the static properties are determined by a characteristic lengthscale (i.e., l) which is ∝ρ−1/3 in the soft-particle limit. The high frequency elastic moduli of these fluids are examined, which reveals that the mechanical properties become more ‘rubbery’ as the particles get softer.

Graphical abstract: Physical properties of soft repulsive particle fluids

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Publication details

The article was received on 15 Jun 2007, accepted on 20 Aug 2007 and first published on 29 Aug 2007


Article type: Paper
DOI: 10.1039/B709053F
Citation: Phys. Chem. Chem. Phys., 2007,9, 5570-5575
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    Physical properties of soft repulsive particle fluids

    D. M. Heyes and A. C. Brańka, Phys. Chem. Chem. Phys., 2007, 9, 5570
    DOI: 10.1039/B709053F

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