Phase diagram of hard colloidal platelets: a theoretical account

Wensink, H. H.; Lekkerkerker, H. N. W.

doi:10.1080/00268970903160605

Cited by 52 publications

(85 citation statements)

References 37 publications

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“…One should note that the overall appearance obtained for the 2D phase diagram (Fig. 7) markedly resembles that of 3D systems of prolate and oblate ellipsoids, spherocylinders, and cut-spheres with variable aspect ratio (see references 32,[45][46][47] ). In particular, the isotropic-nematic transition line goes up in occupied area (volume) fraction upon decreasing the particle aspect ratio to eventually meet up with a strongly first-order and almost anisometric-independent fluid-solid transition.…”

Section: Discussionmentioning

confidence: 99%

Phase diagram of two-dimensional hard ellipses

Bautista-Carbajal

Odriozola

2014

The Journal of Chemical Physics

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We report the phase diagram of two-dimensional hard ellipses as obtained from replica exchange Monte Carlo simulations. The replica exchange is implemented by expanding the isobaric ensemble in pressure. The phase diagram shows four regions: isotropic, nematic, plastic, and solid (letting aside the hexatic phase at the isotropic-plastic two-step transition [PRL 107, 155704 (2011)]). At low anisotropies, the isotropic fluid turns into a plastic phase which in turn yields a solid for increasing pressure (area fraction). Intermediate anisotropies lead to a single first order transition (isotropic-solid). Finally, large anisotropies yield an isotropic-nematic transition at low pressures and a high-pressure nematic-solid transition. We obtain continuous isotropic-nematic transitions. For the transitions involving quasi-long-range positional ordering, i. e. isotropic-plastic, isotropic-solid, and nematic-solid, we observe bimodal probability density functions. This supports first order transition scenarios.

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Section: Discussionmentioning

confidence: 99%

Phase diagram of two-dimensional hard ellipses

Bautista-Carbajal

Odriozola

2014

The Journal of Chemical Physics

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“…(3) for the present case of aggregating cylinders is provided in Appendix A.Here we only note that the present system, in the limit of high T where polymerization is not effective, reduces to a fluid of hard quasicylinders, where the use of Parsons-Lee factor is justifiable [64,68,69]. Moreover, in the dilute limit (η(φ) → 1) the excluded volume term in Eq.…”

Section: Theorymentioning

confidence: 99%

“…[46] we include the Parson-Lee factor. Indeed, the Parson decoupling approximation satisfactory models the phase diagram of uniaxial hard ellipsoids [63], hard cylinders [64], linear fused hard spheres chains [65], mixtures of hard platelets [66], hard sphero-cylinders [67][68][69], rod-plate mixtures [70], mixtures of rod-like particles [71,72] and mixtures of hard rods and hard spheres [73]. On the other hand, Ref.…”

Section: Theorymentioning

confidence: 99%

Self-Assembly of Bifunctional Patchy Particles with Anisotropic Shape into Polymers Chains: Theory, Simulations, and Experiments

2011

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Concentrated solutions of short blunt-ended DNA duplexes, down to 6 base pairs, are known to order into the nematic liquid crystal phase. This self-assembly is due to the stacking interactions between the duplex terminals that promotes their aggregation into poly-disperse chains with a significant persistence length. Experiments show that liquid crystals phases form above a critical volume fraction depending on the duplex length. We introduce and investigate via numerical simulations, a coarse-grained model of DNA double-helical duplexes. Each duplex is represented as an hard quasi-cylinder whose bases are decorated with two identical reactive sites. The stacking interaction between terminal sites is modeled via a short-range square-well potential. We compare the numerical results with predictions based on a free energy functional and find satisfactory quantitative matching of the isotropic-nematic phase boundary and of the system structure. Comparison of numerical and theoretical results with experimental findings confirm that the DNA duplexes self-assembly can be properly modeled via equilibrium polymerization of cylindrical particles and enables us to estimate the stacking energy.

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“…33 For monodisperse hard rods, this theory proved successful in accounting for the isotropic-to-nematic phase transition [34][35][36][37] and it was then extended to study mixtures of such particles, 38 also including smectic phases. [39][40][41] For hard discs, the Parsons theory has also been applied, 42,43 but, as it reduces to Onsager theory 44 for thin particles, it does not describe the isotropic-nematic phase transition too well in the thin platelet limit.…”

Section: Appendix: Comparison Between Present Theory and Kirkwood-bufmentioning

confidence: 99%

The effect of size ratio on the sphere structure factor in colloidal sphere-plate mixtures

Cinacchi

Doshi

Prescott

et al. 2012

The Journal of Chemical Physics

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Binary mixtures of colloidal particles of sufficiently different sizes or shapes tend to demix at high concentration. Already at low concentration, excluded volume interactions between the two species give rise to structuring effects. Here, a new theoretical description is proposed of the structure of colloidal sphere-plate mixtures, based on a density expansion of the work needed to insert a pair of spheres and a single sphere in a sea of them, in the presence or not of plates. The theory is first validated using computer simulations. The predictions are then compared to experimental observations using silica spheres and gibbsite platelets. Small-angle neutron scattering was used to determine the change of the structure factor of spheres on addition of platelets, under solvent contrast conditions where the platelets were invisible. Theory and experiment agreed very well for a platelet/sphere diameter ratio D/d = 2.2 and reasonably well for D/d = 5. The sphere structure factor increases at low scattering vector Q in the presence of platelets; a weak reduction of the sphere structure factor was predicted at larger Q, and for the system with D/d = 2.2 was indeed observed experimentally. At fixed particle volume fraction, an increase in diameter ratio leads to a large change in structure factor. Systems with a larger diameter ratio also phase separate at lower concentrations.

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Phase diagram of hard colloidal platelets: a theoretical account

Cited by 52 publications

References 37 publications

Phase diagram of two-dimensional hard ellipses

Phase diagram of two-dimensional hard ellipses

Self-Assembly of Bifunctional Patchy Particles with Anisotropic Shape into Polymers Chains: Theory, Simulations, and Experiments

The effect of size ratio on the sphere structure factor in colloidal sphere-plate mixtures

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