On the linear hard sphere chain fluids

Articles you may be interested inThe isotropic-nematic and nematic-nematic phase transition of binary mixtures of tangent hard-sphere chain fluids: An analytical equation of state J. Chem. Phys. 140, 034504 (2014); 10.1063/1.4860980Isotropic-nematic transition of hard rods immersed in random sphere matrices Phase behavior of semiflexible tangent hard sphere chainsWe present a modification of the generalized Flory dimer theory to investigate the nematic ͑N͒ to isotropic ͑I͒ phase transition in chain fluids. We focus on rigid linear fused hard-sphere ͑LFHS͒ chain molecules in this study. A generalized density functional theory is developed, which involves an angular weighting of the dimer reference fluid as suggested by decoupling theory, to accommodate nematic ordering in the system. A key ingredient of this theory is the calculation of the exact excluded volume for a pair of molecules in an arbitrary relative orientation, which extends the recent work by Williamson and Jackson for linear tangent hard-sphere chain molecules to the case of linear fused hard-sphere chains with arbitrary intramolecular bondlength. The present results for the N -I transition are compared with previous theories and with computer simulations. In comparison with previous studies, the results show much better agreement with simulations for both the coexistence densities and the nematic order parameter at the transition.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The nematic–isotropic phase transition in linear fused hard-sphere chain fluids

Jaffer

Opps

Sullivan

1999

“…5. An improved algorithm have been proposed recently 11,16 which reduces the number of angular integrations, allowing thus for a better accuracy. The calculation of the F M mnl (r) rests on a precise determination of the contact distances between two particles.…”

Section: Resultsmentioning

confidence: 99%

“…12 We finally note that this approximation has been recently successfully extended to nonconvex bodies such as tangent and fused hard sphere chains. 16,11 …”

Section: B the Geometrical Dcfmentioning

confidence: 99%

A theoretical study of the isotropic cut sphere fluids

Chamoux

Perera

1998

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Multidensity integral equation theory for a sticky hard sphere-hard sphere heteronuclear dimer fluid: Thermodynamic and structural properties Integral equation theory for dipolar hard sphere fluids with fluctuating orientational orderThe cut sphere fluid is studied in the isotropic phase by the Percus Yevick ͑PY͒ and the Hypernetted Chain ͑HNC͒ integral equation techniques, as well as by the theory recently proposed which is based on a geometrical interpretation of the direct correlation function. Fluids of cut spheres with thicknesses L* ranging from 0 to 0.7 have been studied, and detailed results for L*ϭ0.1, 0.2, and 0.3 are reported. The L*ϭ0 case is also examined. A new simplified version of the numerical implementation of the PY and HNC closures is proposed here. The results for pressures and structural properties are compared with the available simulations results and the recent theoretical results from the authors. The important feature of the present work is to show the ability of the HNC theory to predict the cubatic phase observed in the computer simulations for thicknesses around 0.2. The nematic phase is also predicted by the HNC theory for thicknesses smaller than L*ϭ0.12. In agreement with previously obtained results, the detailed analysis of the PY theory results show that this approximation is unable to predict an instability toward any of the orientationally ordered fluid phases. The geometrical approach shows the correct trend for an isotropic to nematic transition, but exhibits an instability toward the cubatic phase only for thicknesses above L*ϭ0.5, thus providing an illustration of the inability of standard density functional type theories to fully describe complex fluids. This study also sheds some light on the major differences between the three approaches in the treatment of many body density correlations.

“…The simplest one performs "Ansätze" which relates S λλ ′ (q), or the corresponding direct correlation function c λλ ′ (q), to S(q) or c(q), q = |q| of an appropriately chosen related simple liquid 2,3,4,5,6,7,8,9 . Similar to this is the "Ansatz" for c λλ ′ (q) based on the geometry of two molecules 10,11,12 . The thermodynamical perturbation theory is a systematic approach which uses a liquid system of isotropic particles as a reference and considers the deviation of the particles from sphericity as a perturbation.…”

Section: Introductionmentioning

confidence: 96%

Molecular correlation functions for uniaxial ellipsoids in the isotropic state

Michele

Scala

Schilling

et al. 2006

We perform event-driven molecular dynamics simulations of a system composed by uniaxial hard ellipsoids for different values of the aspect ratio and packing fraction. We compare the molecular orientational-dependent structure factors previously calculated within the Percus-Yevick approximation with the numerical results. The agreement between theoretical and numerical results is rather satisfactory. We also show that, for specific orientational quantities, the molecular structure factors are sensitive to the particle shape and can be used to distinguish prolate from oblate ellipsoids. A first order theoretical expansion around the spherical shape and a geometrical analysis of the configurations confirms and explains such an observation.