Finite-size scaling study of the liquid–vapour critical point of dipolar square-well fluids

Martín-Betancourt, Marianela; Romero-Enrique, J. M.; Rull, Luis F.

doi:10.1080/00268970902889659

Cited by 10 publications

(5 citation statements)

References 38 publications

(55 reference statements)

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“…13). This is also consistent with very recent numerical simulation results 25,26 showing that the addition of a very weak isotropic attraction to the dipolar HS potential makes the condensation transition easily observable.…”

supporting

confidence: 89%

“…It would be interesting to contrast the present results with more realistic models incorporating a competition between an isotropic and anisotropic short range interactions, such as for instance Stockmayer fluids 27 , dipolar Yukawa HS fluids 28 or combination of dipolar and square-well potentials 26 . In spite of its simplicity, the results of the present work suggest that, in the presence of dipolar-like anisotropy, one can continuously tune from situations only affecting the local ordering (such as in the case presented here) to situations where this effect is much more global (such as the real dipolar case), by simply adjusting the range of interaction.…”

Section: For Givenmentioning

confidence: 70%

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confidence: 99%

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Local orientational ordering in fluids of spherical molecules with dipolarlike anisotropic adhesion

2009

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We discuss some interesting physical features stemming from our previous analytical study of a simple model of a fluid with dipolar-like interactions of very short range in addition to the usual isotropic Baxter potential for adhesive spheres. While the isotropic part is found to rule the global structural and thermodynamical equilibrium properties of the fluid, the weaker anisotropic part gives rise to an interesting short-range local ordering of nearly spherical condensation clusters, containing short portions of chains having nose-to-tail parallel alignment which runs antiparallel to adjacent similar chains. 4 have shown that, contrary to an intuitive expectation, gelation of particles with short-range attractions is intimately connected with its equilibrium phase diagram.It is widely believed that the addition of a long-range repulsion to a short-range attraction inhibits phase separation, by promoting the formation of an equilibrium gel. The same mechanism can be achieved by reducing the probability of forming a bulk liquid using the concept of limited-valency and/or patchy particles 2 . This idea has been recently explored by a number of authors, who have used the so-called Kern and Frenkel model with circular adhesive patches (of non-vanishing area), or that with short-ranged attractive point-sites on the surface of hard spheres 5,6,7,8,9,10,11 . In spite of their usefulness, the above models share a common shortcoming on the discontinuous dependence of the potential on the particle orientations, which makes them very difficult to investigate from a theoretical point of view. This drawback is not present in molecular interactions where this dependence is continuous, as for instance in dipolar interactions 12 , a case which is particularly interesting for various reasons. First, because of their widespread appearance in colloidal suspensions, such as ferrofluids, which have important practical applications. In addition, recent studies 13,14,15 have shown the existence of a significant influence, in the equilibrium properties of the fluid, of chain-like aggregation characteristic of the dipolar interaction, which strongly competes with a stable fluid-fluid phase separation.Motivated by this features, in this paper we then take an extreme alternative of considering a tail with dipolarlike anisotropy combined with a very short-range attraction. The latter is patterned after the well-known Baxter's sticky hard sphere (SHS) potential, where attraction occurs only at contact 16 . Building upon our previous, almost fully analytical, study on this model within the Percus-Yevick closure with orientational linearization (PY-OL) 17 , we discuss here some additional interesting features on the local ordering properties, which were not accounted for in our previous work.In the same spirit of Baxter's isotropic counterpart 16 , the model is defined by the following Mayer functionwhere f HS (r) = Θ (r − σ) − 1 is its hard sphere (HS) contribution, Θ the Heaviside step function ( Θ(x < 0) = 0, Θ(x > 0) = 1 ), and the Dira...

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confidence: 89%

Section: For Givenmentioning

confidence: 70%

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Local orientational ordering in fluids of spherical molecules with dipolarlike anisotropic adhesion

2009

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“…One of the longest outstanding questions is whether DHSs exhibit a vapor-liquid transition [5], from the early theoretical analysis by de Gennes and Pincus [6] through to the latest computer-simulation studies by Rovigatti et al [7,8] The consensus from computer simulations is that there is no such transition in DHSs, but that * philip.camp@ed.ac.uk it may arise in the presence of (small) additional interactions such as anisotropic repulsions [9], multipolar interactions [10], isotropic interactions [5,[11][12][13], and interactions mediated by nonpolar particles [14]. Extrapolations of simulation data to the DHS limit yield estimates of the putative critical parameters; at the critical point, the dipolar coupling constant λ = βμ 2 /σ 3 6 where β = 1/k B T , and the particle volume fraction ϕ 0.05 [5,10,13,14]. There are existing theories of DHS thermodynamics such as the mean spherical approximation (MSA) [15,16] and the thermodynamic perturbation theory (TPT) of Stell, Rasaiah, and Narang [17,18] as applied to DHSs by Rushbrooke, Stell, and Høye [19].…”

Section: Introductionmentioning

confidence: 99%

Thermodynamics of dipolar hard spheres with low-to-intermediate coupling constants

Elfimova

Иванов²,

Camp

2012

Phys. Rev. E

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The thermodynamic properties of the dipolar hard-sphere fluid are studied using theory and simulation. A new theory is derived using a convenient mathematical approximation for the Helmholtz free energy relative to that for the hard-sphere fluid. The approximation is designed to give the correct low-density virial expansion. New theoretical and numerical results for the fourth virial coefficient are given. Predictions of thermodynamic functions for dipolar coupling constants λ=1 and 2 show excellent agreement with simulation results, even at the highest value of the particle volume fraction φ. For higher values of λ, there are deviations at high volume fractions, but the correct low-density behavior is retained. The theory is compared critically against the established thermodynamic perturbation theory; it gives significant improvements at low densities and is more convenient in terms of the required numerics. Dipolar hard spheres provide a basic model for ferrofluids, and the theory is accurate for typical experimental parameters λ

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“…Simple models of intermolecular interaction have proven to be useful tools in understanding diverse phenomena in real fluids. Among these, the so-called discrete potentials that include the popular squarewell [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] and square-shoulder [9,[19][20][21][22] potentials, or combinations of them [13,[23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39], have received much attention. This is not surprising in view of their relative simplicity and versatility, which allows one to treat a variety of problems including, amongst others, chemical reactions [24], liquid-liquid transitions [28][29][30]33], colloidal interactions…”

Section: Introductionmentioning

confidence: 99%

Rational-function approximation for fluids interacting via piece-wise constant potentials

Santos¹,

Yuste²,

Haro³

2012

Condens. Matter Phys.

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The structural properties of fluids whose molecules interact via potentials with a hard-core plus n piece-wise constant sections of different widths and heights are derived using a (semi-analytical) rational-function approximation method. The results are illustrated for the cases of a square-shoulder plus square-well potential and a shifted square-well potential and compared both with simulation data and with those that follow from the (numerical) solutions of the Percus-Yevick integral equation.

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Finite-size scaling study of the liquid–vapour critical point of dipolar square-well fluids

Cited by 10 publications

References 38 publications

Local orientational ordering in fluids of spherical molecules with dipolarlike anisotropic adhesion

Local orientational ordering in fluids of spherical molecules with dipolarlike anisotropic adhesion

Thermodynamics of dipolar hard spheres with low-to-intermediate coupling constants

Rational-function approximation for fluids interacting via piece-wise constant potentials

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