Liquid crystal phase diagram of the Gay-Berne fluid

Miguel, Enrique de; Rull, Luis F.; Chalam, Manoj K.; Gubbins, Keith E.

doi:10.1080/00268979100102321

Cited by 287 publications

(151 citation statements)

References 30 publications

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“…The failure of these hard-particle systems to reproduce the density-driven nematic-isotropic transition shown by the equivalent soft particle model is a surprising result; by contrast, the nematic-isotropic transition densities of hard gaussian overlap model [22] are virtually identical to those of the equivalent (soft) Gay-Berne systems [23,24]. Indeed, the failure of our hard 8 pear systems to form nematic phases could be taken as an indication that particle shape did not contribute significantly to the mesophase formation processes seen in Ref.…”

Section: Simulation Resultsmentioning

confidence: 96%

Computer simulations of hard pear-shaped particles

et al. 2003

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We report results obtained from Monte Carlo simulations investigating mesophase formation in two model systems of hard pear-shaped particles. The first model considered is a hard variant of the truncated Stone-Expansion model previously shown to form nematic and smectic mesophases when embedded within a 12-6 Gay-Berne-like potential [1]. When stripped of its attractive interactions, however, this system is found to lose its liquid crystalline phases. For particles of length to breadth ratio k = 3, glassy behaviour is seen at high pressures, whereas for k = 5 several bi-layer-like domains are seen, with high intradomain order but little interdomain orientational correlation. For the second model, which uses a parametric shape parameter based on the generalised Gay-Berne formalism, results are presented for particles with elongation k = 3, 4 and 5. Here, the systems with k = 3 and 4 fail to display orientationally ordered phases, but that with k = 5 shows isotropic, nematic and, unusually for a hard-particle model, interdigitated smectic A 2 phases.2

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Section: Simulation Resultsmentioning

confidence: 96%

Computer simulations of hard pear-shaped particles

et al. 2003

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“…8,12 At high density ͑or pressure͒ the GB system exhibits a layered phase identified as smectic B ͑SmB͒. 6,9,12 Simulations using different combinations of parameters have shown that the GB model exhibits an additional phase identified as smectic A ͑SmA͒. [15][16][17][18] All these simulation studies suggest that the occurrence of the SmB is not very sensitive to the particular parameterization, whereas the formation of the SmA phase requires the molecular elongation be large enough.…”

Section: Introductionmentioning

confidence: 97%

“…The pair interaction between molecules i and j is given by to mimic the anisotropic interactions in an equivalent linearsite Lennard-Jones potential. This parametrization has been widely used in computer simulation to study the phase behavior, liquid crystal properties, [6][7][8][9][10][11][12] and also in theoretical studies. 13,14 For this choice of parameters, the system exhibits phases identified as vapor (V), isotropic (I), and nematic (N), and the regions of stability have been determined by Gibbs ensemble simulation (V -I region͒ 7,11 and thermodynamic integration (I -N region͒.…”

Section: Introductionmentioning

confidence: 99%

The global phase diagram of the Gay–Berne model

Miguel

Vega

2002

The Journal of Chemical Physics

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The phase diagram of the Gay-Berne model with anisotropy parameters ϭ3, Јϭ5 has been evaluated by means of computer simulations. For a number of temperatures, NPT simulations were performed for the solid phase leading to the determination of the free energy of the solid at a reference density. Using the equation of state and free energies of the isotropic and nematic phases available in the existing literature the fluid-solid equilibrium was calculated for the temperatures selected. Taking these fluid-solid equilibrium results as the starting points, the fluid-solid equilibrium curve was determined for a wide range of temperatures using Gibbs-Duhem integration. At high temperatures the sequence of phases encountered on compression is isotropic to nematic, and then nematic to solid. For reduced temperatures below Tϭ0.85 the sequence is from the isotropic phase directly to the solid state. In view of this we locate the isotropic-nematic-solid triple point at T INS ϭ0.85. The present results suggest that the high-density phase designated smectic B in previous simulations of the model is in fact a molecular solid and not a smectic liquid crystal. It seems that no thermodynamically stable smectic phase appears for the Gay-Berne model with the choice of parameters used in this work. We locate the vapor-isotropic liquid-solid triple point at a temperature T VIS ϭ0.445. Considering that the critical temperatures is T c ϭ0.473, the Gay-Berne model used in this work presents vapor-liquid separation over a rather narrow range of temperatures. It is suggested that the strong lateral attractive interactions present in the Gay-Berne model stabilizes the layers found in the solid phase. The large stability of the solid phase, particularly at low temperatures, would explain the unexpectedly small liquid range observed in the vapor-liquid region.

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“…In the last twenty years, the phase diagrams of a number of model systems ͑including solid and liquid-crystalline phases͒ have been obtained by using computer simulation. For example, studies have been carried out for hard ellipsoids, 4 hard spherocylinders, 5 hard cut spheres, 6 hard dumbbells, [7][8][9] quadrupolar hard dumbbells, 10 fully flexible hard chains, 11,12 hard charged spheres, [13][14][15] Gay-Berne molecules, 16,17 and simple point charge model water molecules. 18 The calculation of the complete phase diagram of a proposed model system can now be carried out within a reasonable amount of time due to the increased speed of modern computers.…”

Section: Introductionmentioning

confidence: 99%

The phase diagram of the two center Lennard-Jones model as obtained from computer simulation and Wertheim’s thermodynamic perturbation theory

Vega

McBride

Miguel

et al. 2003

The Journal of Chemical Physics

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The global phase diagram ͑i.e., vapor-liquid and fluid-solid equilibrium͒ of two-center Lennard-Jones ͑2CLJ͒ model molecules of bond length Lϭ has been determined by computer simulation. The vapor-liquid equilibrium conditions are obtained using the Gibbs ensemble Monte Carlo method and by performing isobaric-isothermal NPT calculations at zero pressure. In the case of the solid phase, two close-packed solid structures are considered: In the first structure, the molecules are located in layers and all molecular axes point in the same direction; and in the second structure, the atoms form a close-packed arrangement but the molecular axes of the diatomic molecules have random orientations. It is shown that at the vapor-liquid-solid triple-point temperature, the orientationally disordered solid is the stable structure for the solid phase of this model. The vapor-liquid-disordered solid triple-point temperature of the 2CLJ model, with bond length Lϭ , is located at T*ϭ0.650(4). This is very close to the triple-point temperature of the Lennard-Jones monomer system (T*ϭ0.687). At very low temperatures, the ordered solid is the stable phase. The vapor-ordered solid-disordered solid triple point is situated at T*ϭ0.282. The simulation data are compared to Wertheim's first-order thermodynamic perturbation theory ͑TPT1͒ for the fluid and solid phases. It is found that Wertheim's TPT1 not only provides an accurate description of the equation of state in both the fluid and solid phases, but also provides accurate values of the free energies. The prediction of Wertheim's TPT1 for the global phase diagram of the 2CLJ model shows excellent agreement with the simulation results, illustrating the possibility of using Wertheim's perturbation theory to determine not only the vapor-liquid equilibria but also the global phase diagram of simple chain model molecules.

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Liquid crystal phase diagram of the Gay-Berne fluid

Cited by 287 publications

References 30 publications

Computer simulations of hard pear-shaped particles

Computer simulations of hard pear-shaped particles

The global phase diagram of the Gay–Berne model

The phase diagram of the two center Lennard-Jones model as obtained from computer simulation and Wertheim’s thermodynamic perturbation theory

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