Transport coefficients of soft repulsive particle fluids

Heyes, D. M.; Brańka, A. C.

doi:10.1088/0953-8984/20/11/115102

Cited by 10 publications

(23 citation statements)

References 35 publications

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“…To take into account the effect of a change of the diameter σ, it was suggested to use the relation: Although this normalization reduced the deviation, it did not make the coefficient c constant. The study of the Stokes -Einstein relation in the soft sphere system [24][25][26] also confirmed the deviation from both above formulas.…”

Section: Stokes -Einstein Relationsupporting

confidence: 67%

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Transport coefficients of soft sphere fluid at high densities

2012

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320Knowledge of transport properties of matter at high pressures and high temperatures is extremely impor tant. One of obvious examples of liquid at high pres sure and high temperature is Earth outer core which is supposed to be liquid. However, nowadays it is not possible to carry out any experiments at such extreme conditions. The extreme conditions region is also hard for theoretical investigations and simulation studies. Importantly, all theoretical models are developed for normal conditions, and we can never be sure that the same models are applicable at high pressure and tem perature. Basing on this speculation it becomes impor tant to carry out a systematic study of some simple model in wide range of pressures and temperatures in order to see the most important effects induced by pressure and temperature. Such investigation will give a solid base for studies of more complex and more realistic systems.In this work we choose a soft spheres system as a generic model for high pressure atomic systems. This system is defined by the interaction potential (1) where ε and σ are energy and length scales. This sys tem is convenient for our goals since its thermody namic quantities follow well known scaling laws [1][2][3][4][5]). An important consequence of this scaling is that the soft spheres phase diagram is one dimensional, and it is known at all temperatures. This allows us to carry out simulations up to very high temperatures and pres sures being sure that the system is in stable liquid phase. ¶ The article is published in the original.Obviously, soft sphere system is a toy model of a real liquid. However, at high pressures and tempera tures the behavior of substances is mostly governed by repulsive cores atoms. This makes soft spheres one of the simplest qualitative models of matter at extremely high temperatures and pressures.It is well known that the thermodynamic properties of the soft sphere system can be expressed in terms of a reduced parameter, γ = ρσ 3 (k B T/ε) -3/n , where ρ is the reduced number density (ρ = N/V, for N particles in volume V), k B is the Boltzmann constant and T is the temperature (Klein theorem [1-3]). It may be shown [1-5] that the following scaling laws are valid along the melting line (we skip the Boltzmann con stant in the formulas below for the sake of brevity):(2)where V 0 , T 0 , and P 0 are some arbitrary values of vol ume, temperature and pressure.The exponents in (2) and (3) were known before (see, for example, [3]). However, in [5] the method was developed which can be applied to any physical quantity of the form F = under the trans formation which preserves the form of Hamiltonian equations. This transformation conserves geometric relations on a phase trajectory, thereby preserving the scaling of the individual trajectories of each of the N particles and, hence, it conserves the multiphase nature of the whole system. The simplest example of a phase equilibrium curve is the two phase meltingMolecular dynamics computer simulation has been used to compute in wide pressure te...

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Section: Stokes -Einstein Relationsupporting

confidence: 67%

“…where σ is the diameter of a particle and c is the constant which equal 2 for "stick" boundary conditions and 3 for the "slip" ones [17]. Several authors studied the Stokes -Einstein coefficient c in different systems [22][23][24][25][26]. The deviation from the Stokes -Einstein law was found.…”

Section: Stokes -Einstein Relationmentioning

confidence: 99%

Transport coefficients of soft sphere fluid at high densities

2012

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“…Thus, in later work, η*(V*) was parameterised by considering the experimental data for normal alkanes; this led to a representation of η*(V*) by an eight-term polynomial in (1/V*) valid in the interval 1.5 ≤ V* ≤ 5, corresponding to the normal liquid range of many substances [7]. Recent molecular dynamics calculations for smooth hard spheres provide much improved results [20][21][22] which we considered further below.…”

Section: The Hard-sphere Modelmentioning

confidence: 99%

Extended hard-sphere model for the viscosity of dense fluids

Ciotta

Trusler

Vesovic

2014

Fluid Phase Equilibria

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“…A drop in viscosity with increasing softness has been reported for particles interacting with soft potentials. 39,40 Fig 2a. Zero-shear rate relative viscosity η r,0 versus volume fraction ϕ c for bare and 5% w/w silica particles in PEG-400.…”

Section: Soft Matter Accepted Manuscriptmentioning

confidence: 99%

Impact of small changes in particle surface chemistry for unentangled polymer nanocomposites

et al. 2015

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We report microstructural and rheological consequences of altering silica particle surface chemistry when the particles are suspended in unentangled polyethylene glycol with a molecular weight of 400. The particle surfaces are altered by reacting them with isobutyltrimethyoxysilane. Levels of silanization are chosen so that the particles remain dispersed in the polymer at all volume fractions studied. Our studies indicate that at the levels studied, silanization does not alter the hydrodynamic thickness of the absorbed polymer layer thickness. Rheological properties are not sensitive to levels of silanization up to particle volume fractions where the average particle separation h ∼ 6Rg (4.8 nm). At these volume fractions, composite microstructure undergoes changes associated with jamming of soft particles (decorrelations in the first peak of the particle structure factor and the onset of a non-diffusive mechanism that dominates particle density fluctuations at short times.) In the region of volume fractions where h/Rg < 6, the zero-shear rate viscosity of the composites is extremely sensitive to level of silanization with a decrease in the zero-shear rate viscosity by four orders of magnitude observed for the highest levels of silanization studied in comparison to the bare particles.

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Transport coefficients of soft repulsive particle fluids

Cited by 10 publications

References 35 publications

Transport coefficients of soft sphere fluid at high densities

Transport coefficients of soft sphere fluid at high densities

Extended hard-sphere model for the viscosity of dense fluids

Impact of small changes in particle surface chemistry for unentangled polymer nanocomposites

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